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University Microfilms International 300 N. ZEEB RD., ANN ARBOR, Ml 48106 8214149
Tuggle, Benjamin Noel
A STUDY OF GIZZARD NEMATODES AND RENAL COCCIDIOSIS IN CANADA GEESE (BRANTA CANADENSIS INTERIOR) OF THE MISSISSIPPI VALLEY POPULATION
The Ohio State University Ph.D. 1982
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University Microfilms International A STUDY OF GIZZARD NEMATODES AND RENAL COCCIDIOSIS IN CANADA GEESE
(BRANTA CANADENSIS INTERIOR) OF THE MISSISSIPPI VALLEY POPULATION
DISSERTATION
Presented in Partial Fulfillment of the Requirements for
the Degree Doctor of Philosophy in the Graduate
School of the Ohio State University
By
Benjamin Noel Tuggle, B.S., M.S.
*****
The Ohio State University
1982
Reading Committee:
ohn L. Crites
Theodore Bookhout Approved By
Loren Putnam
Adviser Malcolm McDonald 'partment of Zoology ACKNOWLEDGMENTS
I give thanks to Almighty God for my life and the accomplishment of this goal. To my family I give my deepest appreciation for the support, understanding, and inspiration that was given to me through out my academic career; this achievement is dedicated to you.
My utmost gratitude is given to Dr. John L. Crites who patiently guided me through my graduate training. Few men have inspired me more and for his benevolence I will always be thankful.
To Dr. Malcolm McDonald, Dr. Milton Friend, and the other members of the National Wildlife Health Laboratory I give my thanks for their role in the initiation and completion of this study. To
Richard Hunt, Dr. Scott Craven, Dr. Donald Rusch, Dr. A. J. Stewart and the Ontario Ministry of Natural Resources, and the members of the Illinois Department of Natural Resources at Union County and
Horseshoe Lake wildlife refuges I give thanks for their help in collecting specimens. I am also thankful for the constructive comments given by Dr. Theodore Bookhout and Dr. Loren Putnam regarding this text. A special thanks to Dr. Ronald Fayer for his aid in interpreting the endogenous stages of renal coccidia.
I am especially grateful for the moral support that was given to me by all my friends, 1 could not have done it without you all.
This study was funded by the U.S. Department of Interior, U.S.
Fish and Wildlife Service.
ii VITA
November 1 3, 1953 . Born - Fort Benning, Georgia
1974 - 1975 . . . . Research Assistant, Department of Biology, Fort Valley State College, Fort Valley, Georgia
1975 ...... B.S. Biology, Fort Valley State College, Fort Valley, Georgia
1975 - 1976.... Fellowship, The Ohio State University, Columbus, Ohio
1976 - 1978.... Teaching Associate, Department of Zoology, The Ohio State University, Columbus, Ohio
1977 ...... M.Sc. Zoology, The Ohio State University, Columbus, Ohio
1978 - 1979 . . . . Research Assistant, Commercial Fisheries Research and Development Project
1979 - present . . Diagnostic Parasitologist, National Wildlife Health Laboratory, Madison, Wisconsin.
PUBLICATIONS
"The occurrence of Postharmostomum helicis in Anguispira kochi strontiana." Ohio J. Sci. 78:9, abstr. 1978
"Parasites of the Bald Eagle, Haliaeetus leucocephalus, of North America" J. Wildl. Dis. In press. 1982
FIELDS OF STUDY
Major Field: Parasitology
Studies in Fisheries and Wildlife Parasitology. Professor John L. Crites
Studies in Avian Parasitology. Dr. Malcolm E. McDonald
iii TABLE OF CONTENTS
Page ACKNOWLEDGMENTS ...... ii
VITA ...... ill
LIST OF TABLES ...... vi
LIST OF FIGURES ...... x
INTRODUCTION ...... 1
METHODS AND MATERIALS ...... ' ...... 7
GIZZARD NEMATODES ...... 13
HISTORICAL REVIEW OF GIZZARD NEMATODES ...... 14
TAXONOMY OF GIZZARD NEMATODES ...... 18
Genus Amidostomum ...... 20 Amidostomum anserls ...... 21 Amidostomum spatulatum ...... 23 Genus Epomidiostomum ...... 27 Epomidiostomum crami ...... 27
LIFE HISTORY OF AMIDOSTOMUM A N S E R I S ...... 30
RESULTS ...... 33
Prevalence of Gizzard Nematodes ...... 34 Mean Worm Burdens of Gizzard Nematodes ...... 43 Abundance Indexes for Gizzard Nematodes .... 49 Analysis of Variance ...... 56 Total Numbers of Gizzard Nematodes ...... 58 Pathological Effects of Gizzard Nematodes . .-. 60 Gizzard Nematodes in Lesser Snow Geese .... 66
DISCUSSION ...... 69
RENAL COCCIDIOSIS ...... 76
HISTORICAL REVIEW OF RENAL COCCIDIOSIS ...... 77
RESULTS ...... 85
Description of Eimeria clarkei ...... 86
iv TABLE OF CONTENTS (continued)
Page Pathological Effects of Elmeria clarkei ...... 89 The Prevalence of Eimeria clarkei ...... 104
DISCUSSION ...... 108
CONCLUSION ...... 120
BIBLIOGRAPHY ...... 124
v LIST OF TABLES
Table Page
1. Sex and age composition of Canada geese collected from three locations in the Mississippi Flyway, 1979-1981 ...... 9
2. Prevalence of gizzard worms in different sex and age groups of MVP Canada geese by worm species, 1979-1981 37
3. Prevalence of gizzard worms in male MVP Canada geese sampled at each location by worm species, 1979-1981 ...... 38
4. Prevalence of gizzard worms in female MVP Canada geese sampled at each location by worm species, 1979-1981 38
5. Prevalence of gizzard worms in immature MVP Canada geese sampled at each location by worm species, 1979-1981 39
6. Prevalence of gizzard worms in adult MVP Canada geese sampled at each location by worm species, 1979-1981 39
7. Prevalence of gizzard worms in all MVP Canada geese sampled at each location by worm species, 1979-1981 41
8. Prevalence of gizzard worms in MVP Canada geese of individuals sex and age groups at each location compared by years, 1979-80, 1980-81 ...... 41
9. Prevalence of single, dual and triple infections with each species of gizzard worms in immature, adult and combined age groups of MVP Canada geese, 1979-1981 ...... 42
10. Mean worm burdens (standard deviations) of gizzard worms in different sex and age groups MVP of Canada geese by worm species, 1979-1981 46
vi LIST OF TABLES (continued)
Table Page
11. Mean worm burdens (standard deviations) of gizzard worms in male MVP Canada geese sampled at each location by worm species, 1979-1981 ...... 48
12. Mean worm burdens (standard deviations) of gizzard worms in female MVP Canada geese sampled at each location by worm species, 1979-1981 48
13. Mean worm burdens (standard deviations) of gizzard worms in immature MVP Canada geese sampled at each location by worm species, 1979-1981 50
14. Mean worm burdens (standard deviaitons) of gizzard worms in adult MVP Canada geese sampled at each location by worm species, 1979-1981 ...... 50
15. Mean worm burdens (standard deviations) of gizzard worms in all MVP Canada geese sampled at each location by worm species, 1979-1981 ...... 51
16. Mean worm burdens (standard deviations) of gizzard worms in MVP Canada geese of individual sex and age groups at each location compared by years, 1979-80, 1980-81 ...... 51
17. Abundance indexes of gizzard worms in MVP Canada geese of different sex and age groups by worm species, 1979-1981 ...... 53
18. Abundance indexes of gizzard worms in male MVP Canada geese sampled at each location by worm species, 1979-1981 ...... 54
19. Abundance indexes of gizzard worms in female MVP Canada geese at each location by worm species, 1979-1981 54
vii LIST OF TABLES (continued)
Table Page
20. Abundance indexes of gizzard worms in immature MVP Canada geese sampled at each location by worm species, 1979-1981 ...... 55
21. Abundance indexes of gizzard worms in adult MVP Canada geese sampled at each location by worm species, 1979-1981 ...... 55
22. Abundance indexes of gizzard worms in all MVP Canada geese sampled at each location by worm s p e c i e s ...... 57
23. Abundance indexes of gizzard worms in individual sex and age groups of MVP Canada geese sampled at each location compared by years, 1979-80, 1980-81 ...... 57
24. Total numbers of gizzard worms (percent immature) in different sex and age groups of MVP Canada geese by worm species, 1979-1981 ...... 59
25. The sex and age ratios of each gizzard worm species and the ratios for total gizzard worms in MVP Canada geese, 1979-1981 ...... 61
26. The prevalence of each gizzard worm species and the prevalence of dual and triple infections in lesser snow geese from WInisk, Ontario, 1979-1980 ...... 67
27. List of published records of free-flying avian species with renal coccidiosis ...... 80
28. Species of waterfowl in which renal coccidiosis (Unknown species) has been found by Malcolm E. McDon a l d ...... 82
29. Age or sex groups of MVP Canada geese showing total numbers infected with Eimeria clarkei, 1979-1981 106
viii LIST OF TABLES (continued)
Table Page
30. Individual age and sex groups of MVP Canada geese showing total numbers infected per group and number (percent) shedding oocysts of Eimeria clarkei, 1979-1981 ...... 106
ix LIST OF FIGURES
Figure Page
1. The migration route of the Mississippi Valley Population of Canada geese showing their nesting area in upper Ontario and their wintering areas in east-central Wisconsin and southern Illinois . . 5
2. Total numbers of Canada geese collected from each sampling area in the Mississippi Flyway, 1979-1981 8
3. An en face view of Amidostomum anseris ...... 22
4. Anterior end of Amidostomum a n s e r i s ...... 24
5. The spicules of Amidostomum a n s e r i s ...... 24
6. Anterior end of Amidostomum spatulatum ...... 26
7. The spicules of Amidostomum spatulatum ...... 26
8. Anterior end of Epomidiostomum c r a m i ...... 29
9. The spicules of Epomidiostomum crami ...... 29
10. The life history of Amidostomum a n s e r i s ...... 31
11. The prevalence of Amidostomum anseris, A. spatulatum, Epomidiostomum crami and overall gizzard worms in MVP Canada geese examined, 1979-1981...... 35
12. The mean worm burden of Amidostomum anseris, A. spatulatum, Epomidiostomum crami and overall gizzard worms in MVP Canada geese examined, 1979-1980 ...... 44
13. The mean worm burdens of total gizzard worms in MVP Canada geese at each collection area and the overall burden in all areas combined, 1979-1981...... 47
14. Amidostomum sp. in the mucosal lining of the gizzard from a MVP Canada g o o s e ...... 63
x LIST OF FIGURES (continued)
Figure Page
15. Gross view of a MVP Canada goose gizzard in cross-section showing lesions caused by Epomidiostomum crami ...... 63
16. Epomidiostomum crami in association with a granulomatous capsule in the gizzard muscle from a MVP Canada g o o s e ...... 65
17. The ova of Epomidiostomum crami in the gizzard muscle from a MVP Canada g o o s e ...... 65
18. The oocyst of Eimeria c larkei ...... 86
19. The endogenous stages of Eimeria clarkei infecting kidney tubule cells of a MVP Canada goose ...... 87
20. An endogenous stage of Eimeria clarkei in the cytoplasm of a tubule cell of a MVP Canada goose ...... 88
21. Endogenous stages of Eimeria clarkei in a MVP Canada gose showing parasite cell types one (Pi) and two (P2) ...... 88
22. Extracellular endogenous forms of Eimeria clarkei in a MVP Canada goose showing different parasite cell types, type one (Pi) and type two (P2) ...... 90
23. Type one (Pi) and type two (P2) endogenous forms of Eimeria clarkei in a MVP Canada g o o s e ...... 90
24. The endogenous stages of Eimeria clarkei from the kidney of a MVP Canada goose showing types one (Pi) and (P2) ...... 91
25. Gross view of a MVP Canada goose kidney infected with Eimeria clarkei ...... 94
xi LIST OF FIGURES (continued)
Figure Page
26. Eimeria clarkei oocysts in wet smear taken from a MVP Canada goose kidney ...... 95
27. Extracellular Eimeria clarkei oocysts (0) and endogenous (E) forms occurring in the interstitial tissue of a MVP Canada goose kidney ...... 95
28. The accumulation of Eimeria clarkei oocysts in a kidney tubule of a MVP Canada goose ...... 96
29. Intracellular endogenous forms and young oocysts (P) of Eimeria clarkei in the kidney of an adult MVP Canada g o o s e ...... 98
30. Macrophage (M) response in a MVP Canada goose kidney to extracellular endogenous stages (P) of Eimeria clarkei ...... 100
31. An endogenous stage (P) of Eimeria clarkei occupying the cytoplasm of two MVP Canada goose kidney tubule cells ...... 100
32. Young oocysts (0) of Eimeria clarkei rupturing the cytoplasmic membranes of tubule cells from a MVP Canada goose...... 101
33. Total numbers of MVP Canada geese infected with Eimeria clarkei at each collection area in the Mississippi Flyway ...... 105
xii INTRODUCTION
The Canada goose, Branta canadensis interior, of the Mississippi
Valley Population (MVP) has been the subject of several detailed research studies in an effort to better manage this species as a wildlife resource. During recent years the numbers of Canada geese using available wintering areas in the United States have increased dramatically, thus refuge managers have had to contend with increased numbers of birds on limited amounts of land. One such area is Horicon National Wildlife Refuge in east-central
Wisconsin where goose use has increased from zero in 1946 when the refuge was established to peak fall populations of 225,000 birds in
1975.
In 1976, the U.S. Fish and Wildlife Service and the Wisconsin
Department of Natural Resources implemented programs to alleviate the known and potential problems that are associated with increased fall concentrations of Canada geese in east-central Wisconsin. One of the most recognized problems associated with large concentrations of geese was the potential impact of parasites and diseases which might affect the population adversely as their levels increased on these primary resting and wintering grounds. However, no data was available to adequately provide information on potentially pathogenic parasites that might become more prevalent as goose numbers escalated in these areas.
1 2
Information regarding parasites in MVP Canada geese is relatively sparse. Most of the available literature concerns geese that overwinter in southern Illinois. Hanson and Gilford
(1961) provided the only information on the prevalence of helminth parasites in Canada geese that winter in Illinois. Their study, however, did not provide data on parasite burdens in those geese nor did they examine the pathological effects of any specific parasite recovered. Other studies of parasites involved surveys of the microfilariae (Hanson et al, 1956; Hanson, 1956), haemoprotozoa
(Levine and Hanson, 1953), and coccidia (Levine, 1952; Hanson et al,
1957) that occur in MVP Canada geese from southern Illinois.
These studies were mostly surveys of parasites that occur in the goose population and did not provide information on specific parasitic diseases. There are no data on the parasites species in this population of geese specifically for Horicon or any other location
(other than southern Illinois) in the flyway. Therefore, the need for information regarding potential parasitic diseases in geese using Horicon Refuge and other areas in the flyway was recognized.
A comprehensive study of all parasite species occurring in
Canada geese of this flyway was not attempted; rather I intended to study potentially pathogenic monoxenous parasite species with short incubation periods. These factors would aid the rapid transmission of the parasites from host to host in high density areas. Such a density-dependent relationships coupled with the potential pathological effect of these parasites on their host were major considerations prior to choosing parasite species to study. For these reasons, I chose to study gizzard nematodes and renal coccidia in MVP Canada geese. 3
Amidostomiasis and renal coccidiosis have long been recognized
for their disease potential in domestic waterfowl, but little is
known of their occurrence in MVP Canada geese. Hanson and Gilford
(1961) reported the occurrence of the gizzard worm Amidostomum
anseris in Canada geese in southern Illinois but they did not
investigate the pathology caused by this helminth. The gross
pathology caused by A. anseris in gizzards of Canada geese was
examined by Herman and Wehr (1954). Although their study dealt
with the same subspecies of Canada goose, it was conducted over 25
years ago and concerned a different population in the Atlantic
Flyway. Both studies were conducted at site-specific locations,
thus did not offer comparisons of data on gizzard worms collected
from Canada geese from different locations within their respective
flyways.
Renal coccidiosis in domestic and wild birds can cause severe kidney damage that may result in the death of the birds. Although much is known about its pathological effects on the kidney, very
little is known about the disease's prevalence and distribution in wild birds, and the species of protozoa that cause the disease.
Perhaps the best known renal protozoan that causes disease in
geese is Eimeria truncata. However, most of the knowledge of
the disease is concerned with domestic geese rather than wild
geese. This species has been reported only in Canada geese of the
Atlantic and Pacific flyways (Levine, 1973). The presence or absence of this species and the disease needed to be determined
because of the epizootic potential of renal coccidiosis in MVP
Canada geese. 4
For better understanding of these specific parasite problems at Horicon, it was proposed that the geese also be sampled from other locations. This would permit a comparison of the occurrence of the disease at Horicon and various other locations throughout the flyway.
No one has conducted studies which examine gizzard worms and renal coccidia in MVP Canada geese of different sex and age groups collected from their breeding and wintering grounds. Thus, I proposed that 48 Canada geese (12 of each sex and age group) from the nesting area in Canada, from Horicon, and from the wintering grounds in southern Illinois be collected and sampled over a 2-year period (Figure 1). Such a sample would permit a comparison of gizzard worm and renal coccidia infections in different sex and age classes at different geographical locations in the MVP.
The prevalence and intensity of these parasites and their effect on different ages and sexes of definitive hosts have been known to fluctuate with season and habitat in other species. In this study I examined the fluctuations in gizzard worm and renal coccidia infections in MVP Canada geese throughout the migration route of this subpopulation. This study also provides baseline data on these parasites in geese from the breeding grounds prior to their fall migration to the wintering grounds.
The objectives of this study were to: 1) determine what species of gizzard worms occur in MVP Canada geese; 2) determine if renal coccidiosis occurs in MVP Canada geese and, if so, what species cause the disease; 3) determine the prevalence and intensity of gizzard worms and renal coccidia infections in Canada geese Figure 1. The migration route of the Mississippi Valley Population of Canada geese, their nesting areas in upper Ontario and their wintering areas in east-central Wisconsin and southern Illinois. 6 over time and determine the geographic distribution of these parasites in the MVP; 4) determine if differences exist in gizzard worm and renal coccidia infections in MVP Canada geese of different sex and ages; 5) determine the gross and microscopic pathological effects of these parasites in MVP Canada geese; and 6) provide any information on possible relationships that may exist between the prevalence and intensity of gizzard worm infections and/or renal coccidiosis in MVP Canada geese and goose densities at site-specific locations. METHODS AND MATERIALS
A total of 309 Canada geese, Branta canadensis Interior, was
collected from three locations in the Mississippi Flyway: Winisk,
Ontario, Horicon National Wildlife Refuge, Wisconsin, and southern
Illinois (Figure 1). These areas were selected because they were the main stopping areas of Canada geese of the Mississippi Valley
Population during migration.
The northernmost area where birds were collected was Winisk,
Ontario, which is located on the breeding grounds of the interior race of Canada geese. A total of 69 geese was collected from this area in early September of 1979 and 1980 (Figure 2). In 1979,
22 birds were collected from this area (Table 1), 3 immature males,
3 immature females, 8 adult males, and 8 adult females. In 1980,
47 birds were collected, 12 immature males, 11 immature females, 12 adult males and 12 adult females. All of the birds collected for examination were hunter-killed.
The intermediate area where geese were collected was Horicon
Wildlife Refuge, Wisconsin, where the geese usually spend 2 to 4 months in the fall after leaving the breeding grounds. The birds at this location were collected by using a cannon net. A total of
144 geese was sampled at Horicon during the 2-year period of the study (Figure 2). The collections at Horicon were divided into two periods, early fall and late fall. The early fall collection was taken in early October as the geese started to arrive from the 8
TOTAL = 309
i
Figure 2. Total numbers of' Canada geese collected from each sampling area in the Mississippi Flyway. 9
Table 1. Sex and age composition of Canada geese collected from three locations in the Mississippi Flyway, 1979-1981.
Month Immature Adult Collection Site and Year Males Females Males Females Tota]
Winisk, Ontario 9/1979 3 3 8 8 22
Winisk, Ontario 9/1980 12 11 12 12 47
Horicon Refuge 10/1979 6 6 6 6 24 (early sample)
Horicon Refuge 11/1979 12 12 12 12 48 (late sample)
Horicon Refuge 10/1980 6 6 6 6 24 (early sample)
Horicon Refuge 11/1980 12 12 12 12 48 (late sample)
Union County 2/1980 12 12 12 12 48 Refuge
Horseshoe Lake 2/1981 12 12 12 12 48 Refuge
Total 75 74 80 80 309 10 breeding grounds. The late fall collection was taken in mid-November as the birds prepared to migrate to their wintering grounds.
In 1979, the early fall collections was taken because all of the scheduled samples were not obtained at Winisk due to poor hunter success. I assumed that because the birds had just arrived from their breeding grounds they would be carrying the same parasites they acquired there. A total of 24 birds was collected during this sample, 6 of each age and sex (Table 1).
In 1980, the early sample was taken to maintain continuity, the same number of geese were taken. The late fall sample was taken in mid-November so that the birds had time to feed on the grounds. Forty-eight geese, 12 of each sex and age, were taken for this sample period in 1979 and 1980.
The third area of collection was at the wintering grounds in southern Illinois, at Union County Refuge in 1980 and at Horseshoe
Lake Refuge in 1981. The geese were collected with a swim-in trap in February of both years before they migrated northward to the breeding grounds. Forty-eight geese, 12 of each sex and age, were collected in 1980 and 1981 (Table 1). The methods described by
Hanson (1949, 1962) were used to sex and age geese.
Gizzards and kidneys were removed from the geese. Gizzards were removed with proventriculi intact, placed in whirl-pac plastic bags, labeled with the bird's number, sex, age, and collection location, after which they were frozen. One of the two kidneys was placed in a whirl-pac bag and frozen, the other kidney was fixed in 10% formalin. The labeling procedure was the same as described for the gizzards. 11
The gizzards and proventriculi, when thawed, were examined with a dissecting microscope to find helminths in the epithelial
lining or under the koilin (horny layers). The two tendons holding
the halves of the gizzard muscle together were cut and the contents were washed into a pan and examined for lead shot or helminths in
the lumen of the gizzard. The mucosal lining and koilin were examined for erosion, necrosis and discoloration. The worms collected
from the mucosal lining and from under the koilin were counted,
fixed in AFA (alcohol-formalin-acetic acid), cleared in glycerin and later identified. The areas of the gizzard where the worms occurred were also noted. Helminths were identified to species,
their sex and stage of development recorded, and placed in labeled vials containing 70% glycerine-alcohol.
Microscopic examination of wet smears of thawed kidney tissue were made to detect coccidian oocysts. At least five smears were made from different regions of each kidney and examined at 140 and
1000X magnification using a light microscope. Histological sections were made of the anterior, medial and posterior portion of each fixed kidney to detect coccidian oocysts and developmental stages.
Tissue was sectioned at 5 yusing standard histological procedures, then stained with hematoxylin-eosin and Giemsa stains.
Oocysts found in wet smears were measured with an occular micrometer. Developmental stages and oocysts seen in histological
sections were measured by the same method.
Large numbers of unsporulated oocysts were teased from the
tissue of frozen and unfrozen infected kidneys, placed in Petri
dishes containing a thin layer of 2.5% potassium dichromate (I^C^Oy) 12 and in dishes containing 1-day old tap water and then left at room temperature for 7 to 21 days to induce sporulation. The oocysts were examined at 24-hour intervals.
Gizzards and kidneys from 24 lesser snow geese, Chen caerulescens caerulescens, were collected from Winisk in 1979 and 1980 to compare them with the Canada geese collected from the same area. They were also hunter-killed birds. The same procedure used to examine
Canada goose gizzards and kidneys were used to examine these organs collected from the snow geese.
Statistical analysis of data was conducted at the Academic
Computing Center at the University of Wisconsin at Madison. Analysis of variance tests were performed to detect finite factors and their interactions which would have significant probabilities of effecting the prevalence, intensity, and abundance of each species of gizzard nematode and their overall total in MVP Canada geese, at a confidence level of 0.05. The following factors and interactions were tested to determine which effects had the most significant statistical fit: age, sex, zone, year, age-sex, age-zone, age-year, sex-zone, sex-year, zone-year, age-sex-zone, age-sex-year, age-zone-year, and sex-zone-year.
Representative specimens of each species of gizzard worm and histological sections of renal coccidia found in Mississippi Valley
Canada geese were deposited in the Parasite Collection of the
National Wildlife Health Laboratory in Madison, Wisconsin. GIZZARD
NEMATODES
13 HISTORICAL REVIEW OF GIZZARD NEMATODES
Gizzard worms have been known to cause disease in domestic
geese for many years. In the early 1900's the disease was referred
to as "Magenwurmseuche" or gizzard worm disease in Germany and was
reported to cause significant mortality in domestic goose flocks
throughout Europe. Amidostomum anseris was the nematode species
with which early researchers identified the disease, and its severe
infestations led to pathology in the gizzard that contributed to high mortality in domestic flocks.
Cram (1925) first reported A. anseris in North America when
she noted that it caused heavy mortality in large numbers of domestic geese in New York. Following Cram's initial report other researchers reported the occurrence of A. anseris and amidostomiasis in domestic geese throughout North America (Jerstad, 1936; Adler and Moore,
1948; Farr and Wehr, 1952; Oliver, 1952; McCraw, 1952).
Much research has been conducted in regards to the pathology
caused by gizzard worms because of their effect on domestic geese.
The majority of the data reported concerns A_. anseris because of its frequent occurrence and high worm burdens in its hosts. When Cram (1926) found the nematodes in the lining of the gizzard of domestic geese in New York, she reported that geese with heavy infections became emaciated and anemic and lost their appetites. The gizzards of infected birds displayed necrotic, crumbling horny layers which had deposits of brown pigment resulting from hemorrhages.
14 15
Bunyea and Creech (1926) also studied the pathological significance of gizzard worm disease in domestic geese. They found that _A. anseris affects the gizzard in three major ways: by the mechanical migration of the worms which causes ulcerations and hemorrhages throughout the mucosa, by the hosts absorption of toxic by-products released by the parasite, and by helping to establish an area for secondary bacterial infection. They also noted that the presence of the worms was associated with brown pigment deposits in the mucosal lining at the base of the horny layers accompanied by necrosis of the layers and separation of the mucosal lining throughout the organ.
From histological studies Bunyea and Creech (1926) reported that the presence of the parasite in the mucosal lining of the gizzard was marked by small hemorrhages throughout and a very noticeable infiltration of macrophages and inflammatory cells.
They also pointed out that young geese show the most visible signs of the disease when they are heavily infected and that in mild cases of infection there is little damage to the gizzard.
Amidostomum sp. was first reported from the Canada goose by
O'Roke (1928). Later Wickware (1930) reported A. anseris in Canada goose goslings that died in western Ontario. After these initial reports of the nematode in Canada geese, other researchers also reported its occurrence (Jerstad, 1937; Wickware, 1941; Herman and Wehr, 1954; Cowan and Herman, 1955; Herman iet a^L, 1955;
Hansen et al, 1957; Hanson and Gilford, 1961; McDonald, 1974b).
Wehr (1933) first reported A. spatulatum in Canada geese, and
Epomidiostomum crami was first reported from this host by Wetzel
(1931). These species are regarded as parasites that primarily 16
inhabit the gizzards of snow geese, and have not been reported in
Canada geese as frequently as A. anseris*
From 1949 through 1956, C. M. Herman, E. E. Wehr, M. M. Farr,
and several others investigated the recurring reports of losses of
Canada geese of the Atlantic flyway on their wintering grounds
centering around Pea Island National Wildlife Refuge, North Carolina.
The studies were conducted primarily to determine the factors
contributing to the high mortality in the wintering flocks at that
location but a great deal of information concerning the parasites
of Canada geese was collected as well.
Herman and Wehr (1954) stated that jjl. anseris was the most
common parasite in Canada geese and occurred in 98% of the geese
examined at Pea Island. They found that Canada geese Infected with
even small numbers of A. anseris had some evidence of gizzard lining
erosion but the extent of its occurrence was not consistent. Extensive
erosion was present when the number of worms exceeded 150. Herman
et al (1955) reported that in Canada geese with heavy infections of
A. anseris, the gizzard was almost completely denuded of its lining
and in such individuals complete loss of normal function of the gizzard was evident. Herman and Wehr (1954) also postulated that Amidostomum was more of a contributing factor to the winter losses than a
primary cause by itself.
Cowan and Herman (1955) reported that sick birds examined from
Pea Island had an average worm burden of 119.6 gizzard worms, whereas healthy controls from the same location carried an average of only
24.7 worms with a 98% prevalence in each group. They suggested
that factors such as malnutrition, adverse weather conditions, and 17 heavy infestation with A. anseris and other parasites were probably
the most important factors that contributed to the sickness and death of Canada_.geese at Pea Island. Amidostomum anseris was the only gizzard worm they identified in the geese examined during those studies.
The only study of gizzard worms in Canada geese of the Mississippi
Valley Population was done by Hanson and Gilford (1961). Unlike the Pea Island studies, they did not find as high a prevalence of gizzard worms in MVP geese. They recovered a single species of gizzard worm, A. anseris, occurring in 32.1% of 639 geese from
Horseshoe Lake Refuge in southern Illinois. They also reported that infection rates and mean worm burdens were higher in immature geese than in adult geese.
McDonald (1974b) surveyed several subspecies of Canada geese of the Central and Pacific flyways and reported three species of gizzard worms. He found an 87.5% prevalence of A., anseris, the prevalence was twice as high in immature geese as in adults. The immature birds also had the highest mean worm burden at 24.5 worms as compared to 13.5 worms per adult goose. McDonald (1974b) also reported a low prevalence of A. spatulaturn in Canada geese (< 5%) and he found a much higher prevalence occurred in snow geese (> 50%).
He also reported a 39.1% prevalence of Epomidiostomum crami in
Canada geese that he examined. The pathology caused by A. spatulaturn and E_. crami in the gizzards of Canada geese is not discussed in the literature. Prior to his report, only A. anseris had been reported in Canada geese of North America with any frequency. TAXONOMY OF VENTRICULAR NEMATODES
The genus Amidostomum was established in 1909 by Railliet and
Henry, but after its establishment there was some disagreement as to the superfamily in which the genus should be placed. The combination of a chitinized buccal capsule as seen in strongylid type nematodes and the morphological similarities with trichostrongylid types caused the disagreement in classification of the genus among helminthologists. Railliet and Henry placed Amidostomum in the family Strongylidae under the superfamily Strongyloidea.
Seurat (1918) placed the genus Amidostomum in the family
Trichostrongylidae, established by Leiper in 1912. He did so because he thought they were closer to the trichostrongyles.
Travassos in 1920 proposed the subfamily Amidostominae and placed it in the family Strongylidae because the members of the genus
Amidostomum possessed a buccal capsule. York and Maplestone (1926), agreeing with Seurat, adopted Travassos' subfamily but grouped it with the Trichostrongylidae. Also, in the same year Baylis and
Daubney (1926) elevated the subfamily Amidostominae to the family
Amidostomidae and included the genera Amidostomum, Epomidostomum, and Amphiliophilus.
Cram (1927) conferred on the family Trichostrongylidae the status of a superfamily Trichostrongyloidea, and placed the family
Amidostomidae and subfamily Amidostominae in her new superfamily.
She stated that the presence of a reduced buccal capsule in a
18 19 bursate nematode similar to other trichostrongyles suggested that
Amidostomum may be a transitional form between the trichostrongyles and the group of strongyles with a buccal capsule. Cram also placed the genus Epomidiostomum, established by Skrjabin in 1915, in the subfamily Amidostominae because of its similarities with
Amidostomum.
Travassos (1937) changed his opinion and agreed with Cram, arguing that the subfamily Amidostominae does belong with the
trichostrongyles because the buccal capsule in Amidostomum reaches a rather limited degree of development and all other features resemble the trichostrongylids. However, he ignored Cram's super family Trichostongyloidea and the family Amidostomidae and placed the subfamily Amidostomidinae in the family Trichostrongylidae. He also placed Epomidiostomum in the subfamily Epomidiostomatinae, within the same family.
Russian helminthologists did not agree with Cram and the others. In 1937, Skrjabin and Schulz (cited in Skrjabin et al, 1954) accepted the superfamily Trichostrongyloidea but removed the family
Amidostomidae from this group and placed it in the superfamily
Strongyloidea. Stressing the taxonomic importance of the presence of the buccal capsule, they concluded that the latter superfamily should include the family Amidostomidae because the genus Amidostomum possesses a definite chitinized oral cavity. They also removed the genus Epomidiostomum from the family Amidostomidae and placed it in the subfamily Epomidiostominae, under the family Trichostrongylidae.
They did so because they felt the members of the genus were true trichostrongyles having well-developed bursa and lacking a buccal capsule. 20
Most helminthologists today agree that both genera belong in
the Trichostrongyloidea but they may differ as to the family in
which they should be placed. Yamaguti (1961) did not recognize
the family Amidostomidae but recognized the subfamily Amidostominae.
He placed the subfamily under the family Trichostongylldae and put
both Amidostomum and Epomidiostomum in the subfamily Amidostominae.
Grasse' (1965), however, disagreed with Yamaguti, and accepted the
family Amidostomidae and suggests that both genera should be grouped
in this family. Chitwood (1969) agreed with Yamaguti on the classification
of the two genera, and it is that classification that is accepted here.
The classification of gizzard nematodes encountered during
this study is as follows:
Phylum Nematoda Class Secernentea Order Strongylida Suborder Trichostronglina Superfamily Trichostrongyloidea Family Trichostrongylidae Subfamily Amidostominae Genus Amidostomum species anseris species spatulaturn Genus Epomidiostomum species crami
Genus Amidostomum
The characteristics of the genus Amidostomum as given by Yamaguti
(1961) are as follows:
Amidostomum Railliet and Henry, 1909
Generic diagnosis. --- Amidostominae: Mouth directed straight forward; buccal capsule sub- globular, with a sharp tooth or teeth in its depth. Esophagus with three axial chitinous plates extending practically whole length of its lumen. 21
Male: Bursa with lateral lobes much longer than dorsal lobe; ventrovental and lateroventral rays widely separate, three laterals separate, externodorsal arising separately from dorsal, dorsal divided near its extremity into two short digitate branches; spicules equal, each divided for more than half its length; gubernaculum elongate. Female: Vulva in posterior fifth of body; tail digitiform. Parasitic in gizzard of birds. Genotype: Amidostomum anseris (Zeder, 1800) Railliet and Henry, 1909
The genus Amidostomum was reviewed by Czaplinski (1962), who noted that some 17 species of Amidostomum were reported in the literature as of 1960. He, however, synonymized many of them and suggested that only 6 true species exist. McDonald (1974a) listed
9 species of Amidostomum that occur in birds worldwide.
Amidostomum anseris
The description of Amidostomum anseris as given by Cram (1927), all measurements given in descriptions are in microns unless otherwise designated:
Amidostomum anseris (Zeder, 1800) Railliet and Henry, 1909
Specific diagnosis. Amidostomum: Anterior end enlarged, with 2 pairs of large submedian papillae; short wide buccal capsule with 3 teeth at base, and ridges throughout its length [Figure 3]. Male: 10 to 17 mm long, 0.25 to 0.35 mm wide; bursa with 2 large lateral lobes, small median lobe; pair of large papillae on posterior lip of cloacal opening; ventro-ventral and latero-ventral rays curved forward, reaching margin; externo- lateral and externodorsal rays not reaching margin; dorsal ray short, doubly forked; with origin in dependent of other rays; spicules 280-300 long, cleft near middle, internal branch with spatulate tip; gubernaculum slender, 95 long. Female: 12 to 24 mm long; 0.3 to 0.4 mm wide at vulva; vulva transverse slit, 160 long, some times covered by projecting appendix, 1/5 of body length from posterior end; tail elongate, straight, bluntly pointed. Eggs thin-shelled, 100-110 by 66-82; embryonated when deposited. 22
Figure 3. An en face view of Amidostomum anseris. Note the teeth (T), papillae (P), and the ridges (R) around the buccal capsule. 23
Czaplinski (1961) reported that A. anseris was first vaguely
described by Froelich in 1791, and he, not Zeder 1800, should have
been regarded as the author of this species, which was first named
A. mucronatum (Froelich, 1791). Zeder in his description of anseris confused two genera, Amidostomum and Epomidiostomum.
Froelich, on the other hand, in his description of A. mucronatum
described only one worm. In 1803, Rudolph! described the worm
previously described by Froelich, ignoring that previous description and Zeder's description because he confused two genera; he called his species A. nodulosum. When the genus was proposed in 1909 by
Railliet and Henry they used A. anseris (Zeder, 1800) as the type
species. However, Seurat in 1918 suggested using A. nodulosum
(Rudolphi, 1803) as the type because Zeder had confused two genera.
Cram in 1927 disagreed with Seurat and pointed out that under the zoological code Amidostomum is fixed by its type and thus Seurat's
type is invalid. Thus the species name A. anseris was kept even
though Frolich described the worm initially.
A. anseris is a euryxenous parasite with worldwide distribution and infecting host species in the Anseriformes, Gru^iformes, Podiciped- iformes, and Columbiformes. Figures 4 and 5 show the anterior end and the male spicules.
Amidostomum spatulatum
The description of Amidostomum spatulatum is taken from Baylis
(1932) and is as follows:
Amidostomum spatulatum Baylis, 1932
Specific diagnosis. Amidostomum: Males: 15 to 16.2 mm long; 220-240 maximum thickness. Figure 4. Anterior end of Amidostomum anseris. Note the oral papillate (P) and the teeth (T) in the buccal capsule.
Figure 5. The spicules (S) of Amidostomum anseris. 25
Anterior end dorsally and ventrally with 2 pairs of small epaulette-like lappets, each corresponding with a submedian papilla. Buccal capsule rather wide and shallow, 175-225 long, 425-475 maximum (outside) diameter; 3 well-developed teeth from base of capsule, dorsal considerably larger than others; Esophagus 1.5-1.8 mm long, measured from anterior extremity of head; cervical papillae 550-570 from anterior end; excretory pore at about same level; nerve ring 360-430 from anterior end. Only externo dorsal and antero-lateral rays of bursa fail to reach edge; rather pronounced blunt projection on posterior side of postero-lateral ray near its base. Spicules 260-280 long, each divided distally; dorsal process smaller and ends in large laterally flattened expansion with dorsal promi nence; larger ventral process ends in large laterally flattened expansion of roughly triangular outline with rounded angles from lateral view. Accessory piece rather irregularly fusiform or canoe-shaped, 130-140 long. Female: 22 to 26.2 mm long; 270 to 330 max imum diameter. Head as in male. Buccal capsule 525-575 maximum outside diameter. Esophagus 2.1-2.2 mm long, cervical papillae 680-720 from anterior end. Tail 400-410 long, distally bent ventrally at obtuse angle; bears pair of small papillae about 200 from end. Vulva 4600-5500 from posterior end, with body usually swollen at this point; combined length of ovejectors, includ ing sphincters, 500-700. Eggs 87.5-97.5 by 55-65.
Since its initial description (Baylis, 1932), this species has been readily identifiable by its morphological characteristics.
There are no species other than A. spatulatum in the genus Amidostomum that possess the "epaulette-like lappets" formed by cuticular expansions on the anterior end. These epaulettes around the oral cavity (Figure 6) and the heavily chitinized spicules (Figure 7) that this species possesses are excellent diagnostic features and were used to differentiate A. spatulatum from A., anseris when encountered in this study. A. spatulatum has been reported in anseriform birds from North America, Europe, and Eurasia. Figure 6. Anterior end of Amidostomum spatulatum. Note the teeth (T) and epaulette-like lappets (L) around the oral cavity.
‘ /S' '3 \ ‘''T ' v‘, "i*'
Figure 7. The spicules (S) of Amidostomum spatulatum. 27
Genus Ep omi diostomum
The characteristics for this genus are taken from Yamaguti (1961) and are as follows:
Epomidiostomum Skrjabin, 1915
Generic diagnosis. --- Amidostominae: Mouth directed straight forwards. On the dorsal and ventral surfaces of the head is a pair of poster iorly directed nodules (epaulettes) with blunt extremities, on each side is a pair of lateral papillae. Buccal capsule short. Three axially arranged chitinous lamellae within esophagus. Male: Bursa with two lateral lobes and a smaller dorsal lobe; ventral rays parallel, externo-lateral close to other laterals which are fused proximally; externodorsal short, arising at base of dorsal, dorsal divided terminally into two short bidigitate branches. Two large sessile papillae on posterior lip of cloaca. Spicules short, equal, terminating in three branches; gubernaculum absent. Female: Body abruptly tapered behind anus into digitiform process. Vulva behind middle of body. Oviparous. Parasites of gizzard of birds. Genotype: IS. uncinatum (Lundahl, 1848) Seurat, 1918.
A review of the genus was given by Ali (1971). McDonald (1974a) listed 12 species of the genus Epomidiostomum known to occur in anseriform and gruiform birds throughout the world.
Epomidiostomum crami
The species description for Epomidiostomum crami is taken from
Wetzel (1931) and is as follows:
Epomidiostomum crami Wetzel, 1931
Specific diagnosis. --- Epomidiostomum: Body slender, attenuated anteriorly. Cuticle striated, striations highly developed and irregular just behind head. Head 33-36 wide, with cuticular expansion forming 4 head plates; dorsal and ventral plates spheric-triangular, lateral plates wider. Pair of cone-like formations dorsally and ventrally, 8-10 long, extremities pointed and directed subdor- sally and ventrally. Lateral papillae (amphids) prominent and well-developed, each supported by pair of glistening spine-like formations: 4 sub median papillae each terminating in 2 points, less 28
prominent. Mouth opening guarded by 4 tooth-like formations. Mouth cavity funnel-shaped, leading to elongated, club-shaped esophagus. Nerve ring about 300 posterior to head. Male: 9 to 10.5 mm long; maximum width 210-220. Esophagus 1 mm long. Bursa strongly striated, trilobed with extremely small dorsal lobe. Dorsal ray stout, about 75 long, dividing into 2 branches close to distal end, each of which also forks; ex ternodorsal rays with ends rounded. Spicules about 180-200 long, dividing distally into 1 dorsal and 2 subventral branches. Female: 17 to 19 mm long; maximum width of 230 to 240. Esophagus 1.2 mm long. Tail digitiform, narrowing rapidly behind anus; anus about 150 from posterior end; vulva about 3.8 mm from posterior end. Eggs oval, 75-81 by 45-48, thick-shelled.
Epomidiostomum crami was first described by Wetzel (1931). Ali
(1971) proposed that 12. crami was a synonym of ]2. skrjabini Petrov,
1926. Whether this is true has not been determined in this study and, therefore, the nematodes recoverd from Canada geese during this study shall be referred to as 12. crami. The four cone-shaped ornaments present on the head (Figure 8) and the swollen, roughened collar of enlarged cuticular striations just posterior to the head are key diagnostic characteristics in separating this species from other species of this genus. Figure 9 shows the male spicules.
E. crami has been recovered from geese and swans in North America and Asia. 29
Figure 8. Anterior end of Epomidiostomum crami. Note the anterior cuticular ornaments (0) and the cuticular striations (C) behind the head.
Figure 9. The spicules (S) of Epomidiostomum crami. LIFE HISTORY OF AMIDOSTOMUM ANSERIS
Like all members of the family Trichostrongylidae, Amidostomum
anseris is monoxenous and has a direct life cycle. Its life history,
shown in Figure 10, is as follows: Embryonated eggs are passed in
the feces of the host. The first-stage larvae hatch from the eggs
in 24 to 72 hours depending on the temperature and the moisture of
the soil. They undergo their first molt to second-stage larvae
shortly after hatching. The molt of the second-stage larvae to
third-stage, infective larvae occurs from 60 to 80 hours after their
first molt. The time period between molts is temperature dependent.
Second and third-stage larvae are quite resilient, surviving from 7
to 14 days at 6°C, and some larvae frozen in ice become active again
once thawed at room temperature. Both stages are able to swim.
Infective larvae may be ingested while geese are feeding on
land or while they drink water. After ingestion by the host, the
third stage larvae enter the gizzard and burrow into the mucosal
lining where in 2 to 4 hours they exsheath and molt to become fourth-
stage larvae, which undergo a final molt to become adults. The
maturation from third-stage larvae to adult may take between 12 to
30 days with copulation occuring as early as the 12th day post
infection and eggs appearing in the feces in 14 to 25 days. Adults
. may remain with the host for over 18 months. (Taken from Cram,
1931; Cowan, 1955; and Kobulej, 1959.)
30 31
Adult
Figure 10. The life history of Amidostomum anseris. 32
The life cycles of A. spatulatum and Epomidiostomum crami are unknown but because they are also trichostrongyles their life cycles presumably are also direct and probably similar to A. anseris.
Leiby and Olsen (1965), who worked out the life cycles of A. raillieti,
A. skrjabini, and E_. uncinatum, give support to this theory by stating that these species had a definite developmental homology with other trichostronglyles. RESULTS
The gizzards of 309 Canada geese from three locations in the
Mississippi Flyway were examined for gizzard worms. Three species of nematodes were found, Amidostomum anseris, Amidostomum spatulatum, and Epomidiostomum crami. The latter two species had not been previously reported in MVP Canada geese.
The adults and fourth-stage larvae of A. anseris were usually found in the mucosal lining of the gizzard and rarely beneath the koilin. The highest concentration of this species frequently occurred in the epithelial lining between the two horny layers around the duodenal junction. Amidostomum spatulatum adults and fourth-stage larvae were also removed from the mucosal lining of the gizzard as well as from beneath the koilin lining. These nematodes were most frequently found in the area of the gizzard where the mucosal lining comes in contact with the horny layers of the organ. Adult helminths were commonly found with half their bodies in the mucosal lining and the remaining half underneath the koilin. The fourth- stage larvae were generally removed from beneath the koilin.
The third species removed from the gizzard, IS. crami, was most frequently found half exposed or entirely beneath the koilin and some times burrowed into the gizzard muscle. The fourth stage larvae and adults were often found encapsulated in nodules formed in the gizzard muscle just below the horny layers. All of the nematodes of this
33 34 species removed from the mucosal lining or from beneath the koilin were sexually mature. Fourth-stage larvae were only found encapsulated in nodules or burrowed in the gizzard muscle. The total E_. crami counts include only adults and fourth stage larvae that were removed completely intact. The counts do not include nematodes that were encapsulated in the muscle tissue or those helminths that had burrowed so deeply into the muscle that they could not be entirely removed.
Prevalence of Gizzard Nematodes
The prevalence percentage of infection or of gizzard nematode species in different sexes and ages of Canada geese at different geographic locations was examined to determine which nematode species occurred most frequently in each group of geese and at each collection location.
The prevalence of each gizzard nematode species and the prevalence of gizzard worms in the total sampled population of Canada geese examined is shown in Figure 11. Amidostomum anseris had the highest prevalence, infecting 88% of all Canada geese, with A. spatulatum having the second highest prevalence at 47.3% and _E. crami the lowest prevalence at 37.5%. At least one of these three species of nematodes was found in 95.2% of the Canada geese examined.
The prevalence of individual gizzard worm species in different sex and age groups of geese is shown in Table 2. Amidostomum anseris was the most prevalent nematode species in each group infecting 88% of all geese sampled. In individual sex and age groups, immature male geese had the highest prevalence of A. anseris at 93.3%; adult females were most often infected with A. spatulatum and E . crami at 68.4% and 51.9% respectively. om i V Cnd gee xmnd 1979-1981. examined, geese Canada MVP in worms
PREVALENCE 100 25 75 50 ptltm A) Eoiisou rm (C, n oeal gizzard overall and (EC), crami Epomidiostomum (AS), spatulatum iue 1 Te rvlne f mdsou nei (AA), anseris Amidostomum of prevalence The 11. Figure AA C OVERALL EC
35
36
Table 2. Prevalence of gizzard worms in different sex and age groups of MVP Canada geese by worm species, 1979-1981.
Sex and/or age of Host AAa AS EC OVERALL
Im M 93.3 18.7 16.0 93.3
Im F 91.9 40.5 31.1 94.6
Ad M 84.0 59.3 49.4 96.3
Ad F 83.5 68.4 51.9 96.2
All M 88.5 39.7 33.3 94.9
All F 87.6 54.9 41.8 95.4
All Im 92.6 29.5 23.5 94.0
All Ad 83.8 63.8 50.6 96.3
Overall 88.0 47.3 37.5 95.2
aAA = Amidostomum anseris, AS = Amidiostomum spatulatum, EC = Epomidiostomum crami 37
The overall frequency of A. anserls was approximately the
same in female and male geese, but the percentage of infection for
A. spatulatum and E_. crami was somewhat greater in females than
in males. When the prevalences of nematode species in immature
and adult geese are compared, the prevalence of A. anseris in
immature birds is higher, but A. spatulatum and _E. crami were more
than twice as prevalent in adult geese than in immatures. These
data suggest the prevalence of A. anseris decreases with age whereas
the frequency of A. spatulatum and 15. crami increases with age.
The prevalence of overall gizzard worms for each individual sex
and age groups are remarkably similar, being slightly higher in
adult male geese.
Male geese from Winisk had the highest prevalence of infection
of A. anseris and JS. crami, and geese from southern Illinois had
the greatest prevalence of A. spatulatum (Table 3). Male geese from
southern Illinois had the highest overall prevalence of gizzard
wo rms.
Female geese from Winisk had the highest frequency of A. anseris,
as seen in Winisk male geese (Table 4). Horicon and southern
Illinois females had the same prevalence of A. spatulatum, however,
Horicon females had the highest prevalence of IS. crami. Winisk
female geese also had the greatest overall frequency of gizzard wor m s .
The frequency of Amidostomum anseris, A. spatulatum, and
E_. crami was greatest in immature geese collected in southern
Illinois as was the overall frequency of gizzard worms (Table 5). 38
Table 3. Prevalence of gizzard worms in male MVP Canada geese sampled at each location by worm species, 1979-1981.
AA AS EC OVERALL
Winisk 91.4 54.3 40.0 97.1
Horicon 86.3 21.9 34.3 91.8
S. 111. 89.6 56.3 27.1 97.9
Overall 88.5 39.7 33.3 94.9
Table 4. Prevalence of gizzard worms in female MVP Canada geese sampled at each location by worm species, 1979-1981.
AA AS EC OVERALL
Winisk 91.2 50.0 38.2 97.1
Horicon 84.5 56.3 47.9 94.4
S. 111. 89.6 56.3 35.4 95.8
Overall 87.6 54.9 41.8 95.4 39
Table 5. Prevalence of gizzard worms in Immature MVP Canada geese sampled at each location by worm species, 1979-1981.
AA AS EC OVERALL
Winisk 93.1 13.8 .1 93.1
Horicon 88.9 26.4 27.8 91.7
S. 111. 97.9 43.4 29.2 97.9
Overall 92.6 29.5 23.5 94.0
Table 6. Prevalence of gizzard worms in adult MVP Canada geese sampled at each location by worm species, 1979-1981.
AA AS EC OVERALL
Winisk 90.0 80.0 65.0 100
Horicon 81.9 51.4 54.2 94.4
S. 111. 81.3 68.8 33.3 95.8
Overall 83.8 63.8 50.6 96.3 40
Winisk adult geese had the highest prevalence of each of the
three nematode species and the greatest overall prevalence of gizzard worms (Table 6). The highest prevalences of each individual species were seen at three different locations (Table 7). Amidostomum anseris was slightly more prevalent in Winisk geese, A. spatulatum was more prevalent in Illinois birds, and Horicon geese were infected more frequently with IS. crami. The overall prevalence of gizzard worm species was virtually identical at Winisk and southern Illinois.
The prevalences of nematode species in geese of each sex and age at each location by collection years are shown in Table 8. The prevalence of helminths in geese generally increased or remained constant the second year in each group for each area. Winisk and
Illinois immature males and adult males from Horicon were the exception, however, and showed a decrease in the prevalence of nematodes the second year of collection.
Table 9 presents the prevalences of single, dual and triple infections with each species of gizzard worm in immature and adult geese. Single infections of A. anseris in immature and adult birds occurred more frequently than did single infections by
the other two species, occurring in 34% of all geese. The A. anseris -
A. spatulatum combination was the dual infection that occurred most frequently, Infecting 21.7% of all geese sampled. The spatulatum - E_. crami combination was the least frequent infection observed, infecting only 3.2% of MVP Canada geese. Triple infections were observed in 20.1% of all geese examined.
When the prevalence of single species infections in immature geese is compared with adults one finds that single infections with Table 7. Prevalence of gizzard worms in all MVP Canada geese sampled at each location by worm species, 1979-1981.
AA AS EC OVERALL
Winisk 91.3 52.2 39.1 97.1
Horicon 85.4 38.9 41.0 93.1
S. 111. 89.6 56.3 31.3 96.9
Table 8. Prevalence of gizzard worms in MVP Canada geese of individual sex and age groups at each location compared by years, 1979-80, 1980-81.
1979-80 1980-81 OVERALL Immature males % inf. % inf. % inf.
Winisk 100 91.7 93.3 Horicon 88.9 94.4 91.7 S. 111. 100 91.7 95.8
Immature females
Winisk 66.7 100 92.9 Horicon 88.9 94.4 91.7 S. 111. 100 100 100
Adult males
Winisk 100 100 100 Horicon 100 83 91.9 S. 111. 100 100 100
Adult females
Winisk 100 100 100 Horicon 94.4 100 97.1 S. 111. 83.3 100 91.7 42
Table 9. Prevalence of single, dual and triple infections with each species of gizzard worm in immature, adult and combined age groups of MVP Canada geese, 1979-1981.
Im Ad OVERALL % inf. % inf. % inf. Single infections ------AA 53.7 15.6 34.0 AS 0 4.4 2.3 EC 0 3.1 1.6
Dual infections ------AA + AS 18.1 25.0 21.7 AA + EC 12.1 11.9 12.0 AS + EC 1.3 5.0 3.2
Triple infections AA + AS + EC 10.1 29.4 20.1 43
A. anseris were far more frequent in immmatures (53.7%) than in
adults (15.5%). However, lone infections with spatulatum or 13.
crami were not found in any immature geese and single species
infections with these species were observed far less frequently in
adults than only A. anseris infections. The prevalences of single
species infections with A. spatulatum and J3. crami in all geese
were 2.3% and 1.6%, respectively. Generally dual infections of
gizzard nematode species were not as frequent in immature geese as
in adults with the exception of the A. anseris - E_. crami combination
which occurred with virtually the same frequency in both groups.
Triple infections were observed almost three times more frequently
in adults as in immature Canada geese.
Mean Worm Burden of Gizzard Nematodes
The mean worm burden or intensity of infection was calculated
for each sex and age class at each collection location to determine
differences in the mean burdens of each species of nematode and of
each group of MVP Canada geese at the collection areas.
Figure 12 illustrates the mean worm burdens and standard
deviations of individual gizzard worm species and the overall worms
burden in all geese collected from the three sample areas. Amidostomum
anseris showed the highest mean worm burden (7.5 nematodes per
bird) and the greatest standard deviation from the mean (+ 10.7 worms). Amidostomum spatulatum and 13. crami had remarkably similar mean burdens of 3.3 and 2.9, respectively. The overall mean worm burden for gizzard worms was 9.7 + 11.6 worms per goose. om i V Cnd gee xmnd 17-90 Vria lines Vertical 1979-1980. examined, geese Canada MVP in worms . ptltm A) Eoiisou rm (C ad vrl gizzard overall and (EC) crami Epomidiostomum (AS), spatulatum A. ersn sadr deviations. standard represent
MEAN WORM BURDEN 20 10 15 iue 2 Tema ombre o Aiotmmasrs (AA), anseris Amidostomum of burden worm mean The 12. Figure AA AS C OVERALL EC
44
45
Amidostomum anseris had the highest intensity of infection in all
sex and age groups of geese (Table 10). Immature females had the highest burden of A. anseris in individual groups and adult males
carried the greatest intensity of A^. spatulatum. Immature females,
adult males and adult females had similar burdens of E_. crami. The
immature female group was the sex and age class with the greatest
total gizzard worm mean burden. Males and females carried almost
the same burden for each individual species but overall, females
carried one worn more on the average than male geese. Immature
geese had higher burdens of A. anseris but adult birds carried
higher burdens of A. spatulatum and E. crami.
Figure 13 illustrates the mean worm burdens of total gizzard worms in all MVP Canada geese sampled at each specific area and
the overall worm burden in all geese. Geese collected at Winisk were most heavily parasitized by gizzard nematodes as compared with the other collection areas, Horicon geese had the lowest
average worn burdens. The mean worm burdens in geese collected
from Winisk and southern Illinois were greater than the overall
burden in all geese combined.
Male geese were most heavily parasitized with A. anseris at
all locations (Table 11). Winisk males carried the greatest burdens
of A. anseris, A. spatulatum, and overall worm species but Horicon
males were most heavily parasitized with E_. crami. Females differed
from the males in that females collected from southern Illinois
had the highest burden of A. anseris, A. spatulatum, and total
worms, but Horicon females, like Horicon males, also had the greatest
burdens of E. crami (Table 12). 46
Table 10. Mean worm burdens (SD) of gizzard worms in different sex and age groups of MVP Canada geese by worm species, 1979-1981.
AA AS ECOVERALL
Im M 7.4(+ 7.1) 2.6(+ 1.7) 2.4(+ 1.8) 8.5(Hh 7.5)
Im F 10.0(+ 16.8) 3.0(+ 2.8) 2.9(+ 2.6) 11.9(+ 16.9)
Ad M 7.0(+ 9.7) 3.9(+ 3.3) 3.0(+ 4.2) 10.1(+ 11.3)
Ad F 5.6(+ 5.1) 3.2(+ 3.7) 3.0(+ 4.0) 8.9(+ 8.3)
All M 7.2(+ 8.5) 3.7(+ 3.1) 2.9(+ 3.8) 9.2(+ 9.7)
All F 7.8(+ 12.6) 3.1(+ 3.4) 2.9(+ 3.6) 10.2(+ 13.2)
All Im 8.7(+ 12.9) 2.9(+ 2.5) 2.7(+ 2.4) 10.1(+ 13.2)
All Ad 7.2(+ 8.5) 3.5(+ 3.5) 3.0(+ 4.1) 9.4(+ 9.9)
Overall 7.5(+ 10.7) 3.3C+ 3.3) 2.9<+ 3.7) 9.7(+ 11.6) 47
30
25
LU Q cc 20 ID CD
CC 1 t - O 1 5
< ULJ 10
WINISK HORICON S. ILL. OVERALL
Figure 13. The mean worm burdens of total gizzard worms in MVP Canada geese at each collection area and the overall burden in all geese combined, 1979-1981. Vertical lines represent standard deviation. 48
Table 11. Mean worm burdens (SD) of gizzard worms In male MVP Canada geese sampled at each location by worm species, 1979-1981.
AA AS EC OVERALL
Winisk 10.3(+ 14.2) 4.5(+ 4.6) 2.1(+ 1.1) 13.1(+ 15.7)
Horicon 6.8(+ 6.2) 3.3(+ 2.7) 3.5(+ 5.3) 8.5(+ 7.8)
S. 111. 5.5(+ 4.2) 3.0(+ 1.6) 2.5(+ 1.7) 7.5<+ 4.4)
Overall 7.2(+ 8.5) 3.6(+ 3.1) 2.9(+ 3.8) 9.2(+ 9.7)
Table 12. Mean worm burdens (SD) of gizzard worms in female MVP Canada geese sampled at each location by worm species, 1979-1981.
AA AS EC OVERALL
Winisk 9.1(+ 9.8) 3.2(+ 5.5) 2.9(+ 4.3) 11.3(+ 12.5)
Horicon 4.9(+ 7.0) 2.9(+ 2.6) 3.0(+ 3.7) 7.6(+ 7.9)
S. 111. 11.0(+ 18.5) 3.3(+ 2.9) 2.8(+ 2.7) 13.3(+ 18.4)
Overall 7.8(+ 12.6) 3.1(+ 3.4) 2.9(+ 3.6) 10.2(+ 13.2) 49
Comparisons of average worm burdens in immature and adult birds each show that immature geese from southern Illinois had the highest burdens for all three nematode species and total worms whereas adults from Winisk had the greatest burdens for A. anseris,
A. spatulatum, and total gizzard worms (Table 13, 14). Horicon adults had the greatest burdens of E_. crami. Inspection of mean intensity of nematode species in all geese sampled from each area revealed that Winisk geese carried the greatest burdens of _A. anseris, A. spatulatum, and overall worms, but that Horicon geese had the highest burdens of JE. crami (Table 15).
Mean burdens of nematodes in individual sex and age classes of geese at each location by collection year generally increased from 1979-80 to 1980-81 (Table 16). Adult males and females from
Illinois were the exception, adult males showing a slight decrease in burden the second year and adult females showing constant burdens for both years.
Abundance Indexes for Gizzard Nematodes
The abundance index values for gizzard nematodes are arrived at by multiplying the prevalence of infection times the mean worm burden of a group of hosts. This index value gives a more reliable evaluation of the overall abundance of worms in a population than the prevalence or mean burden alone because it standardizes the biases of a disproportionate prevalence or mean worm burden value.
The index is used here to examine and compare the overall abundance of gizzard worm species in specific sex and age groups and collection locations. 50
Table 13. Mean worm burdens (SD) of gizzard worms in immature MVP Canada geese sampled at each location by worm species, 1979-1981.
AA AS EC OVERALL
Winisk 9.3(+ 12.0) 1.8(+ 1.0) 1.0(+ 0) 9.6(+ 11.9)
Horicon 6.6(+7.7) 2.7+ 2.0) 2.3(+ 2.0) 7.8(+ 8.2)
S. 111. 11.2(+ 17.8) 3.2(+ 3.0) 3.4(+ 2.8) 13.7(+ 18.1)
Overall 8.7(+ 12.9) 2.9(+ 2.5) 2.7(+ 2.4) 10.1(+ 13.2)
Table 14. Mean worm burden (SD) of gizzard worms in adult MVP Canada geese sampled at each location by worm species, 1979-1981.
AA AS EC OVERALL
Winisk 10.0(+ 12.4) 4.2(+ 5.2) 2.5(+ 3.1) 14.0(+ 15.4)
Horicon 5.1(+ 5.2) 3.2(+ 2.8) 3.7(+ 5.2) 8.3(+7.5)
S. 111. 4.7(H- 3.3) 3.1(+ 1.8) 2.1(+ 1.5) 6.9(+ 4.0)
Overall 6.3(+ 7.8) 3.5(+ 3.5) 3.0(+ 4.1) 9.4(+ 9.9) 51
Table 15. Mean worm burdens (SD) of gizzard worms in all MVP Canada geese sampled at each location by worm species, 1979-1981.
AA AS EC OVERALL
Winisk 9.7(+ 12.2) 3.9(+ 5.0) 2.5(+ 3.1) 12.2(+ 14.2)
Horicon 5.9(+ 6.6) 3.0(+ 2.6) 3.2(+ 4.4) 8.1(+ 7.9)
S. 111. 8.2(+ 13.6) 3.2(+ 2.3) 2.7(+ 2.3) 10.3(+ 13.6)
Table 16. Mean worm burdens (SD) of gizzard worms in MVP Canada geese of individuals sex and age groups at each location compared by years, 1979-80, 1980-81.
1979-80 1980-81 OVERALL Immature males MWB (SD) MWB (SD) MWB (SD)
Winisk 5.3(+3.2) 10.8(+12.7) 9.6(+11.4) Horicon 7.5(+7.4) 9.1(+6.5) 8.3(+6.9) S. 111. 6.4(+3.3) 8.6(+7.1) 7.5(+5.4)
Immature females
Winisk 6.0(+4.2) 10.1(+14.0) 9.5(+12.9) Horicon 4.3(+3.1) 10.2(+12.3) 7.8(+8.2) S. 111. 19.4(+30.5) 19.8(+15.0) 13.7(+18.1)
Adult males
Winisk 12.6(+8.9) 17.4(+22.4) 15.5(+18.0) Horicon 7.2(+8.7) 8.6(+5.3) 8.7(+8.8) S. 111. 7.5(+3.5) 7.3(+3.3) 7.4(+3.3)
Adult females
Winisk 7.5(+6.5) 15.8(+14.5) 12.5(+12.5) Horicon 8.2(+9.4) 9.3(+6.3) 7.9(+6.2) S. 111. 6.3(+5.4) 6.3(+4.3) 6.3(+4.8) 52
Amidostomum anseris has the highest abundance index of the three species of nematodes, 6.6 (Table 17). This was to be expected because A. anseris was the most prevalent and had the greatest mean worm burden in all groups of geese. Immature females had the highest total index value for A. anseris (9.2) and total overall worms (11.3) of the four sex and age groups. Each of the three species of gizzard worms was more abundant in female geese than in male geese and thus females had the higher overall abundance value.
Immature and adult geese had relatively similar overall abundance values 9.5 and 9.0, respectively, indicating little overall difference in total abundance of gizzard nematodes in both age groups. However, inspection of the values for individuals species, shows a much higher value for A. anseris in immature geese (8.0) than in adults
(5.3), but the adult group had a higher abundance of A. spatulatum and 13. crami. Although the immatures had a greater abundance value for Al. anseris than adults, when the higher values for the other two species in adults were combined with the A. anseris value in this class, the overall abundance of gizzard worms for adults was very close to the total abundance value for immatures.
Males from Winisk had the highest abundance value for Al. anseris, A. spatulatum, and overall gizzard worms, whereas females collected in southern Illinois had the highest values for these three categories (Tables 18, 19). Both males and females collected from Horicon had the greatest abundance of E_. crami. When the abundance indexes of immature geese (Table 20) and adult geese
(Table 21) are examined, one finds that immature birds from Illinois had the greatest abundances of A. anseris, A. spatulatum, E^. crami 53
Table 17. Abundance indexes of gizzard worms in MVP Canada geese of different sex and age groups by worm species, 1979-1981.
AA AS EC OVERALL
Im M 6.9 .5 .4 7.7
Im F 9.2 1.2 .9 11.3
Ad M 5.9 2.3 1.5 9.7
Ad F 4.6 2.2 1.5 8.4
All M 6.4 1.4 1.0 8.8
All F 6.8 1.7 1.2 9.8
All Im 8.0 .8 .6 9.5
All Ad 5.3 2.2 1.5 9.0
Overall 6.6 1.6 1.1 9.3 54
Table 18. Abundance indexes of gizzard worms in male MVP Canada geese sampled at each location by worm species, 1979-1981.
AAAS EC OVERALL
Winisk 9.4 2.5 .9 12.7
Horicon 5.9 .7 1.2 7.8
S. 111. 4.9 1.7 .7 7.3
Overall 6.4 1.4 1.0 8.8
Table 19. Abundance indexes of gizzard worms in female MVP Canada geese sampled at each location by worm species, 1979-1981.
AA AS EC OVERALL
Winisk 8.3 1.6 1.1 11.0
Horicon 4.1 1.7 1.5 7.2
S. 111. 9.9 1.8 1.0 12.7
Overall 6.8 1.7 1.2 9.8 55
Table 20. Abundance indexes of gizzard worms in immature MVP Canada geese sampled at each location by worm species, 1979-1981.
AA AS EC OVERALL
Winisk 8.7 0.2 0.04 8.9 CM Horicon 5.9 0.7 0.6 •
S. 111. 11.0 1.4 1.0 13.4
Overall 8.0 0.8 0.6 9.5
Table 21. Abundance indexes of gizzard worms in adult MVP Canada geese sampled at each location by worm species, 1979-1981.
AA AS EC OVERALL
Winisk 9.0 3.4 1.7 14.0
Horicon 4.9 1.7 2.0 7.9
S. 111. 3.8 2.1 0.7 6.6
Overall 5.3 2.2 1.5 9.0 56 and total worms. On the other hand, adult geese from Winisk had the greatest abundances of A. anseris, A. spatulatum, and total helminths. Horicon adults had the greatest abundance value for JE. crami.
Table 22 shows the abundance indexes of each nematode in all
Canada geese from each location. Winisk birds had the highest values for _A. anseris, A. spatulatum, and total worms but Horicon geese were infected with the greatest, abundance of IS. crami. The index values of ventricular nematodes in each sex and age group from each site are compared by years in Table 23. Each group and location showed increases in the abundance of gizzard worms the second year except adult males from Horicon and southern Illinois which showed a slight decrease the second year.
Analysis of Variance
Tests revealed no significant factors or interactions that affected the prevalence of A. anseris and total gizzard worms in
Canada geese (all probabilities > 0.05). However, the age factor significantly affected the prevalence of _A. spatulatum (0.029) and
IS. crami (0.028). The age-zone interaction (0.0097) had the greatest probability of affecting the intensity of A^. anseris infections in geese, but other factors and interactions such as year (0.011), sex-zone (0.013), age-sex (0.015), age (0.017), zone (0.023), age-sex-zone (0.028) and zone-year (0.032) were also significant.
There were no significant factors or interactions affecting the intensity of A. spatulatum and IS. crami infections. The age-zone interaction (0.039) had the greatest probability of affecting the intensity of total gizzard worms. 57
Table 22. Abundance Indexes of gizzard worms in all MVP Canada geese at each location by worm species, 1979-1981.
AAAS ECOVERALL
Winisk 8.8 2.0 1.0 11.9
Horicon 5.0 1.9 1.3 7.5
S. 111. 7.4 1.8 .9 10.0
Table 23. Abundance indexes of gizzard worms in individual sex and age groups of MVP Canada geese sampled at each location compared by years, 1979-80, 1980-81.
1979-80 1980-81 OVERALL Immature males Value Value Value
Winisk 5.3 9.9 7.8 Horicon 6.7 8.6 7.6 S. 111. 6.4 7.9 7.3
Immature females
Winisk 4.0 10.1 8.8 Horicon 3.8 9.7 6.7 S. 111. 19.4 19.8 19.6
Adult males Winisk 12.6 17.4 15.5 Horicon 8.8 7.2 8.0 S. 111. 7.5 7.3 7.4
Adult females Winisk 7.5 15.8 12.5 Horicon 6.0 9.3 7.7 S. 111. 5.3 6.3 5.8 58
ANOVA tests showed that the age-zone interaction (0.013) had the most significant effect upon the abundance of A. anseris in geese although year (0.016), age (0.016), age-sex (0.03), zone
(0.03), age-sex zone (0.032) and zone-year (0.044) were also highly significant factors and interactions. The most significant factor affecting the abundance of A. spatulatum in geese was age factor
(0.007) but the age-zone (0.038) and age-sex (0.047) also had significant probabilities. There were no parameters with significant probabilities of affecting the abundance of IS. crami. The age-zone interaction (0.01) had the most significant probability of affecting the abundance of total gizzard worms in Canada geese, but year
(0.016), age-sex (0.023), sex-zone (0.029), and zone (0.043) were also parameters with significant effects upon abundance.
Total Numbers of Gizzard Nematodes
Comparison of actual total numbers of gizzard worms from different sex and age groups of geese by worm species showed that A. anseris was the species found in the greatest number (2041) followed A. spatulatum (481) and Eh, crami (338) (Table 24). Amidostomum spatulatum had the largest percentage of fourth-stage larvae (54.7%). The greatest number of total nematodes was found in immature female geese and the least amount was removed from immature males. Chi-square tests performed at 0.05 confidence level showed significantly more
IS. crami and total gizzard worms in female geese than in males but no significant difference in the numbers of A. anseris and A_, spatulatum in males and females. Tests also showed no significant difference between immature and adult geese in the total number of 59
Table 24. Total numbers of gizzard worms (% immature) in different sex and age groups of MVP Canada geese by worm species, 1979-1981.
All JL A A (% Im) AS(% Im) EC(% Im) Worms
Im M 75 516(7.0) 36(44.4) 29(6.9) 581(10.8)
Im F 74 680(13.1) 90(58.8) 66(9.1) 836(17.9)
Ad M 80 468(11.3) 185(48.1) 94(11.7) 747(20.5)
Ad F 80 377(10.3) 170(61.8) 149(12.8) 696(23.4)
All M 155 984(9.1) 221(47.5) 123(11.4) 1338(16.2)
All F 154 1057(12.1) 260(60.8) 215(10.2) 1532(20.4)
All Im 149 1196(10.5) 126(54.8) 95(9.5) 1417(15.0)
All Ad 160 845(10.9) 355(54.7) 243(12.5) 1443(21.9)
Total 309 2041(10.6) 481(54.7) 338(11.3) 2860(18.1) 60
gizzard worms. However, there were significantly more A. anseris
in immature geese than adult geese but significantly more A. spatulatum and E_. crami in adult geese than in immature ones.
With regard to sex and age ratios of gizzard worms in Canada geese, numbers of males and females of A. anseris did not differ significantly
(P>0.05) but significantly more adults than immature fourth-stage
larvae were removed from the gizzards (Table 25). Amidiostomum
spatulatum females significantly outnumbered males and there were significantly more fourth-stage larvae than adult helminths. There was no significant difference in the number of male and female _E. crami, but there were significantly more adults than fourth-stage larvae. When all species are combined, there were significantly more female helminths than males and significantly more adults than fourth-stage larvae.
Pathological Effects of Gizzard Nematodes
The geese examined during this study that were infected with
A. anseris, _A. spatulatum and IS. crami displayed some of the same gross characteristics as those described in domestic geese infected with A^. anseris. However, each of the three species, singularly or in combination, affected the gizzard in different ways. A. anseris, which was usually found in the epithelial lining closest to the duodenal junction, in the majority of birds caused minimal damage to the lining in areas where they were removed. Only when large numbers were present (>80) was there any significant gross damage to the mucosal lining and rarely was there a separation of the koilin or crumbling of its edges. 62
On the other hand, A^_ spatulaturn, which was mainly found where
the mucosa and the horny layers meet, caused a substantial amount
of damage to the mucosa. When 40 or more of this species were
present, there was erosion and separation of the koilin from
the mucosal lining of the gizzard. The damage seemed to be localized
around the edges of the horny pads and was most severe when adult worms were present. Fourth stage larvae were found in the same areas where adults were found but they were generally recovered
from beneath the koilin. The damage caused by this species alone was only seen in adult geese (Table 9). Histologically the pathology
caused by Amidostomum sp. in Canada geese gizzards was similar to
the pathology observed in domestic geese. Their presence in the mucosal lining caused hemorrhages throughout the mucosa, macrophage infiltration and a degeneration of the epithelium (Figure 14).
E^. craml in relatively low numbers caused some necrosis in the areas where the mucosa meets the horny layers but usually the damage was minor. The gross pathology associated with lone infections with this species under such circumstances was similar to that of
A. spatulaturn although not as severe. These nematodes were usually found completely under the koilin, half exposed in the mucosa, or burrowed into the gizzard muscle where they were often found encapsulated in nodules formed in the muscle tissue.
When large worm burdens (>25) of 15. crami were found in the mucosa and beneath the koilin of the gizzard, there was a progressive separation of the horny layers from the mucosa. When sizable numbers of this species were found in the gizzard muscle, the pathology was most severe. The muscular layers were mottled in appearance and were studded with large numbers of small granulomata, widely 63
Figure 14. Amidostomum sp. in the mucosal lining of the gizzard from a MVP Canada goose.
Figure 15. Gross view of a MVP Canada goose gizzard in cross- section showing lesions caused by Epomidiostomum crami. 64
scattered throughout the muscularis (Figure 15). These granulomata
were primarily linear in shape, although a few appeared roughly
circular, and measured .5 to 2.5 cm wide by 1.5 to 3.5 cm in length.
Microscopically the granulomata consisted of centrally located
portions of well-preserved nematodes or their ova and the surrounding
inflammatory response of the host (Figure 16). The nematodes appear to
lie in the lumen of minute, tortuous tracts and were usually surrounded
by extravascular erythrocytes, macrophages, and a proliferating
connective tissue wall. The tissue reaction surrounding the parasite
foci consisted of a zone of reactive macrophages, occasional giant
cells (syncytial cells) and fibroblasts which increased in maturity
from the inside of the granulomatous capsule to the junction with normal smooth muscle.
In some granulomata the nematodes had apparently died and undergone fragmentation and the extravascular erythrocytes and macrophages were degenerated, resulting in a central core composed
of fragments of the nematode, degenerative blood cells, and a mass
of acellular debris. This necrotic mass was usually separated from
the surrounding connective tissue capsule by a 1 or 2 cell
thick layer of epitheloid cells. Much of the muscle tissue had been replaced by fibrous tissue.
In portions of the tracts containing E. crami ova, rather than
the nematode itself, there appeared to be little or no extravascular ization of erythrocytes around the ova; however, there was a marked proliferative response by the adjacent connective tissue resulting in the encapsulation of many of the ova (Figure 17). In some areas helminths were noted within spaces in the muscle tissue which 65
Figure 16. Epomidiostomum crami in association with a granu lomatous capsule in the gizzard muscle from a MVP Canada goose.
Figure 17. The ova of Epomidiostomum crami in the gizzard muscle from a MVP Canada goose. 66
failed to elicit more than a very early cellular response to their presence. These nematodes were thought to have recently migrated into these areas. Both adult and fourth-stage larvae were observed in the granulomata and migrating throughout the tissue. The damage to the gizzard was most severe when large numbers of IS. crami were present with large numbers of A. spatulaturn. This combination was most frequently observed in adult Canada geese (Table 9).
Gizzard Nematodes in Lesser Snow Geese
Each of the nematode species found in the gizzards of Canada geese was also found in snow geese, but the latter species was more heavily parasitized. A 100% prevalence of infection with gizzard worms was observed in snow goose gizzards examined. The prevalence of each helminth species and the prevalence of dual and triple infections are shown in Table 26. Amidostomum anseris and
A. spatulaturn had the same prevalence, infecting 83.3% of the birds, but Epomidiostomum crami had the highest prevalence, infecting
91.7% of all snow geese. The A. anseris - 15. crami and the A. spatulaturn - 15. crami combinations had the same prevalence of infection (16.7%) and were the dual infections which were found most frequently. The above two combinations of infection were twice as frequent as A. anseris - A. spatulaturn infections. The low prevalence of this dual Infection in snow geese may be due to competition between these helminths. The high prevalence of this combination in Canada geese would indicate that there is less competition between A. anseris and A. spatulaturn in that host species.
Triple infections occurred in 58.3% of all snow geese, which was almost three times as frequent as triple infections seen in Canada geese. 67
Table 26. The prevalence of each gizzard worm species and the prevalence of dual and triple infections in lesser snow geese from Winisk, Ontario, 1979-1980.
Species % inf.
A A 83.3 AS 83.3 EC 91.7
Dual infection ______
AA + AS 8.3 AA + EC 16.7 AS + EC 16.7
Triple infection ______
AA + AS + EC 58.3 68
The mean worm burdens of each gizzard worm species in lesser
snow geese are as follows:
Species MWB ( S .D )
AA 9.6 (+ 10.7) AS 11.2 (+ 9.0) EC 18.8 (+ 13.6) Overall 34.4 (+ 25.1)
On the average more IS. crami nematodes were found in snow geese
than A. spatulatum and A. anseris. The total worm burden of 34.4
nematodes per snow goose was much higher than the 9.7 helminths
per Canada goose. The abundance indexes performed for each nematode
species in snow geese revealed that A. anseris had an index value
of 8.0, A. spatulatum 9.3, and IS. crami 17.2. Each abundance index value for the above nematode species was greater in snow geese with
the exception of _A. anseris.
It was difficult to evaluate the damage caused by any one
species alone because they were always found in combination with
one of the other two species. However, heavy infections with A. anseris and A. spatulatum were similar to those seen in Canada
geese, and caused the same type of pathology. Because 15. crami was the only nematode that invaded the gizzard muscle, the pathology
associated with this species alone was somewhat less difficult to
evaluate. The gross and microscopic lesions caused by E_. crami were very similar to those observed in Canada geese but were far more severe due to the high prevalence and intensity of this species
in lesser snow geese. DISCUSSION
The nematode Amidostomum anseris was by far the most common of
the three helminths removed from the gizzards of Mississippi Valley
Canada geese. Occurrences of Amidostomum spatulatum and Epomidostomum
crami in Canada geese are not new host records for these species, but
their recovery from Canada geese of this flyway represents a new record
for this subpopulation.
Gizzard nematode infections are discussed in terras of abundances of worms because these values best describe the overall infection in the population. The abundance of gizzard worms differed among the four individual sex and age groups. Immature female geese were most heavily infected with gizzard worms and this was reflected in this group's high abundance value for overall gizzard worm species.
Though this group did not have the greatest abundance of A. spatulatum or E^. crami, it had such a great abundance of A. anseris that the sum total of all helminth species gave the group a high total abundance. Although adult male and adult female geese had identical abundances of _A. spatulatum and 12. crami, adult males had the greatest overall abundance of gizzard worms. Immature males had the lowest abundance of gizzard worms.
Cornwell (1966) noted a difference between male and female canvasback ducks in that females were more heavily parasitized with gizzard worms than males. Differences were also observed in the gizzard worm infections in male and female Canada geese. This
69 70
study shows that overall female geese were more heavily parasitized
with gizzard worms than were male geese, and females had the greatest
abundance index values for each of the three species, A. anseris,
A. spatulatum, and 15. crami. Although the total number of A. anseris and A. spatulatum did not differ significantly between male and female geese, the latter were infected with significantly more JE. crami and total gizzard nematodes.
Although significant differences were seen in the total numbers of helminths in the two sex groups, the ANOVA tests showed that the sex factor did not significantly affect gizzard worm infections by itself and was of more significance when it interacted with other factors.
Wehr and Herman (1954), Halpin (1975) and other researchers have shown that host age is a factor that has a significant affect upon its susceptibility to parasite infections. Cornwell (1966),
Neraasen (1970) and McDonald (1974b) support this concept for gizzard worm infections in other waterfowl. My data showed no significant difference in total numbers of gizzard worms in i mmat u r e and adult geese, but significant differences for individual species in these groups were observed. Little difference was observed in the overall abundance of gizzard worms between immatures and adults, but the abundance of A. anseris was greater in the immature age class than the adult class. On the other hand for A., spatulatum and 15. crami, it was the adult group that had the greatest abundances of these two species. This phenomenon was also observed for the total numbers of these species. Significantly more A. anseris were present in immature geese, but significantly more A. spatulatum and
E. crami were found in adults. 71
The affect of host age upon gizzard worm species was clear.
As age increased, the abundance of A. anseris infections decreased, but the abundance of A. spatulatum and 15. crami infections increased.
ANOVA tests showed the age factor, alone or as an interaction, did significantly affect gizzard worm infections in MVP Canada geese.
These data also showed a difference in abundance of gizzard nematodes between the age groups at each collection area. Immature geese from southern Illinois had the greatest abundance of gizzard helminth species and overall worms for that age class, while Winisk adults had the greatest abundance of A. anseris, A. spatulatum and overall gizzard worms. Gizzard worms acquired by immature geese on the breeding grounds and during their winter migration appeared to be retained, thus the greatest abundances occurred in southern
Illinois immatures. Adult geese however, appeared to acquire the greatest abundances of these parasites while on the breeeding grounds, but then as they migrated southward the overall abundance of nematodes tended to decline.
The host's susceptibility to infection may be one possible explanation. Immature geese had little or no immunity to gizzard worm infection thus helminths acquired were retained. Adult geese, though they showed the highest abundances of gizzard nematodes on the breeding areas, were not as susceptible to reinfection thus abundances of worms decreased.
Epomidiostomum crami infections in adult geese were the lone exceptions, the greatest abundance of this species were found at
Horicon. The data showed that adults infected with this species appeared to acquire large amounts on the breeding grounds, reached 72
a peak in abundance at Horicon and then showed a decrease in E. crami
infections at southern Illinois. Host immunity to reinfection may
also explain this observation.
Wehr and Herman (1954) speculated that geese acquire the
majority of gizzard worm infections while they are on the breeding
grounds. The overall abundance of nematode species found in this
study were very close from area to area. The abundance of overall
gizzard worm species was greater at Winisk, however though the
total number of geese collected there was not as great as other
sample areas* The great abundances of gizzard nematodes in Winisk
geese suggested that the breeding grounds were also the major area
where MVP Canada geese acquired the infections.
Amidiostomum spatulatum and E_. crami infections in Canada
geese were almost certainly acquired on the breeding grounds because
of the large numbers of snow geese that share the area. McDonald
(1974b) regarded the Canada goose as an incidental host for these
nematodes. Neraasen (1970) and McDonald (1974b) examined snow
geese in the western flyways and found that the prevalence and
intensity of A. spatulatum and E_. crami were much higher in snow
geese. Snow geese examined from Winisk also had much greater
numbers of gizzard worm species per bird, and had greater prevalence
of dual and triple infections than Canada geese collected from the
same area. If the population of lesser snow geese does serve as
the major source of infection for these species, then acquisition
by Canada geese would be correlated with the number of times the host returns to the breeding grounds. This would also explain why high abundances were observed in birds from Winisk and why 73
older geese had greater abundances of these species than immature geese. However, these parasites infect geese with such great success that it is also possible that they acquire infective larvae at other locations throughout the flyway.
The breeding grounds may serve as the main area where Canada geese acquire A. spatulatum and 13. crami infective larvae, but it probably is not true of A. anseris infections. I believe that because _A. anseris is such a ubiquitous ventricular nematode and was found in such great numbers in all sex and age groups from all sample areas, the probability of geese acquiring A. anseris infective laravae on either of the wintering areas is just as great as on the breeding grounds.
The ANOVA tests showed that the age-zone interaction and the age factor significantly affected the prevalence, intensity, and abundance of total gizzard worms and individual nematode species in
Canada geese. While the affect of host age upon parasite abundance has been recognized, the ANOVA tests showed that the interaction between age and zone is also of significant importance in determining
the abundance of gizzard nematodes. When none of the tested parameters had a significant effect on the overall abundance of gizzard helminths, the data suggested that all of the factors and interactions had about the same effect, and no one parameter predominated.
Hanson and Gilford (1961) reported that 32.1% of the MVP Canada geese that overwintered in southern Illinois were infected with A. anseris and found a mean intensity of 8.9 helminths per goose. In comparison, my data shows that the prevalence and the mean burden of gizzard nematodes found in geese from southern Illinois has increased, 74
as well as the number of nematode species parasitizing the organ.
The density of geese at southern Illinois has incrased dramatically
since Hanson and Gilford’s initial study. The increased density
at that locaton could be a factor which explains the increase in
gizzard worm abundance.
The pathology associated with gizzard worm infections in MVP
Canada geese can be severe and can be produced by more than one
species. The pathology seemed to be most severe in adult geese
because this age group had the greatest abundances of A. spatulatum
and E^. crami. These species when present even in small numbers
caused significantly more damage to the mucosal lining and koilin
of the gizzard than A. anseris. Each species seemed to inhabit
fairly specific regions of the gizzard and the pathology associated with their presence was somewhat localized. Amidostomum anseris affected the mucosal lining around the duodenal junction, A. spatulatum
infections initiated a separation of the mucosal lining from the horny layers, and 15. crami caused damage not only to the horny
layer but also to the gizzard muscle itself.
Epomidiostomum crami is probably the most pathogenic of the
three nematodes because the adults and fourth stage larvae of this
species invade the muscularis of the gizzard causing hemorrhages and granulomata to be formed in the smooth muscle. The lesions
caused by 15. crami were even more dramatic in the lesser snow geese examined primarily because of the high prevalence and mean worm burdens observed in this host species. When these three helminths were present in the gizzard in large numbers regardless of the
combinations, each species contributed to the overall disease of
the organ. 75
During the study I found that when lead shot pellets were
found in the lumen of the gizzards of Canada geese, no gizzard worms were present. Lead shot pellets were found in a total of
five geese, all from Horicon. The actual effect of lead on the host is well documented, but its effect on the helminth populations
found in the gizzard is still unclear. This study offers nothing more than a speculative correlation between the presence of lead shot and the decrease of gizzard worm burdens. RENAL
COCCIDIOSIS
76 HISTORICAL REVIEW OF RENAL COCCIDIOSIS
Renal coccidiosis was first reported in France by Railliet and
Lucet (1890). They reported that cases of high mortality in domestic goose flocks were caused by a coccidial organism found in the kidney and they named the causative agent Coccidium truncatum, which was later called Eimeria truncata (Railliet and Lucet, 1890)
Wasielewski, 1904. Spiegl (1921) described a similar outbreak in a flock of domestic geese in Germany. He also noted the high mortality in the flock that he was working with and described the kidneys of infected birds as greatly enlarged and containing large numbers of coccidian oocysts. The oocysts he observed were spherical in nature and measured 15 to 20 ym by 13 to 15 ym with a marked microphyle at one end. Spiegl stated that he was unable to sporulate the oocysts. There were several other reports of renal coccidiosis in domestic goose flocks in Europe, each with similar findings (Lerche,
1929; Kotlan, 1933; Walden, 1961; Klimes, 1963).
Renal coccidiosis was first reported in the United States in 1929 by McNutt. He reported 87% mortality among goslings in a domestic flock of geese in Iowa and noted that the first symptoms of the disease in the birds he examined were usually weakness, looseness of bowels, and whitish discoloration of the feces. He also observed that older geese were not affected by the coccidian and appeared
77 78
to be immune to the infection. Although ducks were raised in
areas next to goose pens, they were not affected.
McNutt stated that the kidneys of infected birds were greatly
enlarged and very light in color, showing small nodules, streaks and
lines on the surface throughout the kidney. He called the oocyst
he recovered IS. truncata and after his initial report of this
species in domestic geese in Iowa, other reports of renal coccidiosis
caused specifically by IS. truncata were reported from other parts
of the United States and Canada (Allen, 1933; Wickware, 1941;
Glover, 1947; Adler and Moore, 1948; Levine et al, 1950; Hilbert;
1951; Farr and Wehr, 1952). Pellerdy (1974) described the development
and incidence of E_. truncata, and its pathological effects on the
kidneys of domestic geese.
The first report of renal coccidiosis in wild geese in the
United States was by Critcher (1950) at Pea Island, North Carolina.
He noted that over 500 Canada geese (B. c^. canadensis) died due to
acute infections with IS. truncata coccidiosis. Ducks and snow
geese that shared the wintering area with the Canada geese were not affected. The kidneys of infected birds showed gross lesions
similar to those seen by previous investigators who reported the
disease in domestic geese. Critcher suggested that the high mortality was attributed to renal coccidiosis in conjunction with the high
density of birds using the area and the lack of most desired food plants.
Farr (1954) also investigated mortality in Canada geese during a 5-year period. She found that from 1949 to 1954, 151 of 450 healthy, sick, and dead geese that were examined had 15. truncata 79
infections in the kidneys. Of some 369 birds examined, she found
that 110 were thin and emaciated, 72 of which had kidney coccidia,
54 had moderate to heavy infections, and 46 were in poor condition.
She concluded that because so many healthy birds carried the infection mortality was not due to the renal coccidiosis alone.
Following Critcher's initial report of renal coccidiosis in
Canada geese other investigators found renal protozoan parasites in other wild birds. Table 27 shows the list of free-flying avian species in which renal coccidiosis has been reported in the literature. In most reports in which the coccidia species were identified, the most common species listed was E_. truncata.
In the cases where the coccidia species was unidentified or was listed as Eimeria sp., the author usually found the oocysts and/or developmental stages incidentally in histological sections and reported the pathologic effects caused by the parasite.
For a long period of time virtually every oocyst found in the kidney of a domestic goose or duck, as well as wild birds, was reported as E^. truncata. The symptoms and gross lesions of the infections were similar in most cases, thus when oocysts were found in wet smears they were assumed to be _E. truncata. For example, the fact that the oocysts found by Spiegl and McNutt differed morphologically in size and shape suggests that these two outbreaks could have been caused by two different species of renal coccidosis. There is also the possibility that they were different varieties or strains of the same species which would also account for the variance in their reports. Pellerdy (1974) pointed out that not all of the published reports of birds infected with IS. truncata can be 80
Table 27. List of published records of free-flying avian species with renal coccidiosis.
Host Coccidian Reference
Anas acuta (pintail) Unidentified Wobeser, 1974
Anas platyrhynchos (mallard) 15. boschadis Walten, 1961 Unidentified Wobeser, 1974
Anser anser (greylag goose) 15. truncata Christiansen, 1952 Walden, 1961
Anser indicus E. truncata Venn, 1954 (bar-headed goose)
Branta canadensis E. truncata Critcher, 1950 (Canada goose) Farr, 1954 Hanson ut al, 1957 Walden, 1961
Branta c. leucopareia 15. truncata Greiner et al, 1981 (Aleutian Canada goose) E. clarkei
Chen caerulescens 15. truncata Venn, 1954 (snow goose)
Chen rossii (Ross' goose) E. truncata Hanson et: al^, 1957
Clangula hyemalis 15. somateriae Walden, 1961 (oldsquaw) Unidentified Franson & Derksen, 1981
Cygnus olor (mute swan) E. christianseni Walden, 1961
Gavia immer (common loon) E. gaviae Montgomery et^ a l , 1978
Philohela minor (woodcock) Unidentified Locke j2t a l , 1965
Puffinus tenuirostris Eimeria sp. Munday et^ al^, 1971 (short-tailed shearwater)
Puffinus diomedea Unidentified Munday et al, 1971 (Cory's shearwater)
Somateria mollisima 15. truncata Christiansen, 1952 (common eider) E. somateriae Walden, 1961 81
accepted because some authors may have reported oocysts from the
intestinal content rather than from wet smears or histological
sections of infected kidney tissue.
McDonald (unpublished data) has surveyed many different species
of North American waterfowl for protozoan and helminth parasites.
Table 28 is an unpublished list of bird species in which he found
renal coccidiosis. Many of the species in the list have not been
reported in the literature. McDonald did not sporulate all of the oocysts that he found in the kidneys of the birds, although IS.
truncata and several other species were identified, therefore the host species are listed as having some form of renal coccidiosis.
Hanson eh a]L (1957) commented on the distribution of IS. truncata in wild geese in the United States. They stated that even though
JS. truncata has been found in domestic geese throughout North
America, the species has been reported only in wild geese from the
south Atlantic and Pacific flyways and not the interior flyways.
They surveyed 258 geese from the interior flyways and did not find
E^. truncata or any other species of renal protozoa. They state
(p. 727) that "this difference in distribution of IS. truncata becomes
even more striking when it is considered that it involves two
different populations of the same sub-species of Canada geese,
Branta canadensis interior (referred to as B. c. canadensis by
Critcher, 1950). Those of the south Atlantic flyway, which breed on the Belcher Islands and east of Hudson Bay and James Bay and winter at Pea Island, North Carolina, and other areas of the middle
Atlantic coast, have a high infection rate, but those of the Mississippi
Flyway, which breed west of Hudson Bay and James Bay and winter in 82
Table 28. Species of waterfowl in which renal coccidiosis (unknown species) has been found by Malcolm E. McDonald.
HOST Genus and species Common name
Alx sponsa N. American wood duck
Anas acuta pintail
Anas americana American widgeon
Anas clypeata northern shoveler
Anas crecca carolinensis green-winged teal
Anas cyanoptera cinnamon teal
Anas discors blue-winged teal
Anas platyrhynchos mallard
Anas rubripes black duck
Anas strepera gadwall
Anser albifrons white-fronted goose
Aytha affinis lesser scaup duck
Ay thya americana redhead
Aythya valisineria canvasback
Branta bernicla Atlantic brant
Branta canadensis Canada goose (E. truncata)
Bucephala clangula common goldeneye
Clangula hyemalis oldsquaw
Chen caerulescens greater snow goose
Lophodytes cucullatus hooded merganser
Mergus serrator red-breasted merganser
Olor columbianus whistling swan
Oxyura jamaicensis ruddy duck 83 southern Illinois are uninfected." From this observation, they assumed that renal coccidiosis caused by _E. truncata did not occur in geese of the Mississippi Flyway. Since McDonald did find renal coccidiosis in birds of the Central and Pacific flyways, the lack of the disease in the MVP, if true, would be a gap in what otherwise would appear to be a coast to coast distribution of the infection.
In 1957, Hanson et al also described an unsporulated oocyst that was found in a fecal sample from a lesser snow goose collected from Winisk, Ontario, and named it Elmeria clarkei. At the time of the original description of the oocysts, the target organ for the coccidian was unknown due to the fact it was found in a fecal sample. They described the oocyst as resembling "a round-bottom flask" with a short, narrowed-neck ranging from 25 to 30 ym by 18 to 21 ym, with a mean of 27.3 by 19.3 ym. Hanson ^ £ ^ 1 (1957) pointed out that _E. clarkei oocysts resemble a number of other oocysts in general appearance, but its relative large size and distinctive microphyle separate it from IS. truncata and all other anseriform coccidian species. Their attempts to sporulate the oocysts in
2.5% potassium dichromate were unsuccessful, but they stated that a number of the partially sporulated oocysts contained four sporoblasts, which is the reason they assigned the oocysts to the genus Eimeria.
Prior to this study, IS. clarkei has not been reported in any avian species since its original description, except in the feces of the Aleutian Canada geese, B. c^ leucopareia (Greiner et: al,
1981). The finding of E_. clarkei oocysts and endogenous stages in the kidneys of Canada geese of the Mississippi Flyway for the first time establishes this coccidian as a renal protozoan and significant cause of renal coccidiosis in geese of this flyway.
The taxonomic classification of 13. clarkei is as follows:
Phylum Protozoa Subphylum Apicomplexa Class Telospora Subclass Coccidia Order Eucoccidia Suborder Eimeriina Family Eimeriidae Subfamily Eimeriinae Genus Eimeria species clarkei RESULTS
Description of Eimera clarkei
The microscopic examination of wet smears and histological sections revealed unsporulated oocysts identified as Eimeria clarkei present in infected kidney tissue (Figure 18). This species was the only species of renal protozoa found in the kidneys of 309 Canada geese collected from the Mississippi Flyway. Each of the oocysts found contained a single spherical sporont, somewhat centrally located, with a residura or single granule sometimes present inside the oocysts. The oocyst wall of E^. clarkei is smooth and composed of a single layer approximately 1 to 1.5 pm in width. The oocyst is also characterized by its rounded bottom and its distinctly prominent micropyle.
Mean length and width measurements of 150 oocysts taken from various infected kidneys were respectively, 25.8 m (Range: 22.5 -
27.7 pm) and 18.4 pm (16.6 - 20.9 pm). The sporont had a mean diameter of 11.8 pm (7.5 - 13.2 pm). Attempts to sporulate oocysts found in frozen and unfrozen kidney tissue were unsuccessful.
Eimeria clarkei endogenous stages were also seen in histological sections of goose kidneys (Figure 19). These developmental stages were spherical in shape and were more commonly observed than oocysts.
In young forms there was usually a parasitophorous vacuole surrounding each parasite within the cytoplasm of the infected tubule cell
(Figure 20). These vacuoles were not always present in older forms of the parasite. 85 86
Figure 18. The oocysts of Eimeria clarkei. Note residum (R), sporont (S) and micropyle (M). 87
Figure 19. The endogenous stages of Eimeria clarkei infecting kidney tubule cells of a MVP Canada goose. Note parasite stages (P) within the cell cytoplasm pushing the cell nucleus (N) peripherally. 88
Figure 20. An endogenous stage of Eimeria clarkei in the cytoplasm of a tubule cell of a MVP Canada goose. Note parasite (P), parasitophorous vacuole (V), and cell nucleus (N).
Figure 21. Endogenous stages of Eimeria clarkei in a MVP Canada goose showing parasite cell types, one (Pi) and two (P2)• 89
Two types of stages were observed. One type appeared to have many spherical subunits or granules throughout the parasite cell.
The granules in endogenous stages of this type appeared as tightly bound solid masses of basophilic cytoplasm (Figure 21) or the granules themselves appeared to have distinct circular definition and were distributed throughout the cytoplasm (Figures 22,24). In the latter form, one could see several nuclei within the cytoplasm and beneath the loose clusters of basophilic granules. The second type of stage did not have the basophilic granules distributed throughout the parasites cytoplasm; rather, the granules were smaller and fewer in number and distinctly concentrated in the peripheral regions of the parasite cell (Figures 21,23,24), appearing to form a ring around the somewhat eccentric nuclei.
The mean diameters of developmental stages ranged from 8.4 to
16.2 j^m. In some kidney sections only the endogenous stages of E_. clarkei were observed. In such cases, the identification was based on the size, shape, and appearance of the stages observed and the host cell's response to the presence of the protozoan in its cytoplasm. Commonly both kidneys were infected with oocysts; however, when only endogenous stages were found in the kidneys sectioned histologically, the opposite kidney from the same bird used for wet smears was usually devoid of oocysts. Developmental stages were rarely seen in wet smears because it was difficult to see them when unstained.
Pathological effects of Eimeria clarkei
An infection with IS. clarkei could be described as a latent infection in the majority of the kidneys examined because moderate 90
Figure 22. Extracellular endogenous forms of Eimeria clarkei in a MVP Canada goose showing different parasite cell types, type one (Pi) and type two (P2)»
Figure 23. Type one (Pi) and type two (P2) endogenous stages of Eimeria clarkei in a MVP Canada goose. Note nuclei in type two form. 91
Figure 24. The endogenous stages of Eimeria clarkei from the kidney of a MVP Canada goose showing types one (Pi) and two (P2J* Note the two parasite stages within the cytoplasm of one tubule cell and the position of the cell nucleus (N). 92 93 numbers of oocysts and/or endogenous stages were seen in wet smears and sections, yet grossly the kidney appeared quite normal in color and size.
In the kidneys of two immature males, however, the organs did appear different or "abnormal" grossly. These kidneys were enlarged with whitish streaks and minute foci on the surface of the organ
(Figure 25), and there was apparent urate retention in the kidney tissue. Tremendous numbers of IS. clarkei oocysts were later found in wet smears and histological sections made from tissue of those kidneys (Figure 26). The hypertrophy of the kidney, its mottled color, and the whitish foci located on its surface were attributed to 12. clarkei coccidiosis in the organ.
The pathology associated with IS. clarkei infections was examined histologically using various stains. In the kidney, both stages caused significant damage. The unsporulated oocysts were seen mainly in collecting tubules but also in the interstitial tissue
(Figure 27). In areas where large numbers of oocysts had accumulated, the tubules were markedly distended and the accumulated oocysts caused a rupturing of the cytoplasm of adjacent tubule cells which destroyed the normal tubular architecture (Figure 28). Moderate obstructive effects were also present proximal to these areas.
Collecting ducts were often distended with material resembling partially dissolved urates as well as oocysts. There were areas where pressure necrosis and fibrosis indicative of acute damage were noted in the tissue, particularly near the center of the kidney lobules.
Affected collecting tubules were often surrounded by mononuclear macrophages and inflammatory cells that infiltrated the area from Figure 25. Gross view of a MVP Canada goose kidney infected with Eimeria clarkei. Note the urate retention and the mottled appearance throughout the organ. 95
Figure 26. Eimeria clarkei oocysts in wet smear taken from a MVP Canada goose kidney.
Figure 27. Extracellular Eimeria clarkei oocysts (0) and endogneous stages (E) occurring in the interstitial tissue of a MVP Canada goose kidney. Figure 28. The accumulation of Eimeria clarkei oocysts in a kidney tubule of a MVP Canada goose. Note oocysts (0) within and outside of disrupted tubular structure and the infiltration of macrophages (M). 97 Figure 29. Intracellular endogenous forms and young oocysts (0) of Eimeria clarkei in the kidney of an adult MVP Canada goose. Note the infiltration of macrophages (M). 99 100
Figure 30. Macrophage (M) response in a MVP Canada goose kidney to extracellular endogenous stages (P) of Eimeria clarkei.
Figure 31. An endogenous stage (P) of Eimeria clarkei occupying the cytoplasm of two kidney tubule cells from a MVP Canada goose (N = nuclei). Figure 32. Young oocysts (0) of Eimeria clarkei rupturing the cytoplasmic membranes of tubule cells. Note the early formation of the oocyst wall. 102 103 nearby blood vessels. The infiltration of inflammatory cells was seen particularly in adult birds as they surrounded intracellular and extracellular developmental stages and oocysts (Figures 29,30).
This response was not always seen in immature birds in which the infection was detected.
The endogenous stages of IS. clarkei were most frequently observed in the cytoplasm of renal epithelial cells; however, they were often present in the cytoplasm of mononuclear inflammatory cells as well as extracellularly in the interstitial tissue (Figure 27).
These stages were usually seen one per cell but occasionally two parasite stages were observed in the cytoplasm of one tubule cell
(Figure 23). On some occasions, one stage was seen occupying the cytoplasm of two tubule cells (Figure 31). Once the stages had entered the cell, the parasites started to enlarge within the cytoplasm, pushing the host cell nucleus peripherally and causing the cell to hypertrophy. In areas where infection was evident, there was cellular destruction caused by the maturation of endogenous stage to a young zygote or oocysts, which ultimately resulted in the disruption of the host cell's cytoplasmic membrane
(Figure 32). Infected cells were characterized by an increased cytoplasmic basophilia in association with the endogenous stages of IS. clarkei. The glomeruli of the kidney were uninvolved in the infection.
In November of 1979, a dead Canada goose found at Horicon
National Wildlife Refuge was sent to the NWHL for a detailed necropsy.
The postmortem examination showed the goose's kidneys to be swollen, pale and mottled with whitish foci on the surface much like kidneys 104
infected with JE. truncata. Wet smears made from one kidney contained
enormous numbers of coccidian oocysts, which were identified as _E.
clarkei. The cause of death was diagnosed as massive renal
coccidiosis. This marked the first known case of a goose dying from
renal coccidiosis caused by IS. clarkei. The pathology associated
with the presence of the oocysts and developmental stages was
similar to that described in geese collected for this study but on
a far greater scale. Since the kidneys of this bird were not
frozen, attempts were made to sporulate the oocysts teased from the
tissue. Once again, however, these efforts were unsuccessful.
The Prevalence of Eimeria clarkei
A total of 21 Canada geese was found to harbor the oocysts and/or developmental stages of E^. clarkei or 6.8% of the total
sampled population. Figure 33 shows the distribution and total numbers of infected geese collected in the Mississippi Flyway
during the 2-year period of the study. The sample taken at Winisk had the highest number of infected geese with 8 (11.6%), followed
by the southern Illinois sample with 7(7.3%), and the Horicon
sample with 6 (4.2%).
The number of infected birds differed little between sexes, infected males totaled 11, female birds 10 in number (Table 29).
Chi-square analysis of these data showed no significant difference in male and female birds infected with _E. clarkei (P>0.05). The number of infected birds of each group did differ, however; infected immature geese totaled 15, 71.5% of the total, whereas the 6 adult geese comprised 28.6% of the total number of infected birds. There 105
9
Figure 33. Total numbers of MVP Canada geese infected with Eimeria clarkei at each collection area in the Mississippi Flyway. 106
Table 29. Age or sex groups of MVP Canada geese showing total number infected with Eimeria clarkei, 1979-1981.
Group Number infected
Immature 15
Adult 6
Male 11
Female 10
Table 30. Individual age and sex groups of MVP Canada geese showing total numbers infected per group and number (percent) shedding oocysts of Eimeria clarkei, 1979-1981.
Number Number (percent) Group infected shedding oocysts
Immature males 9 7 (78%)
Immature females 6 4 (67%)
Adult males 2 0 (0%)
Adult females 4 1 (25%) 107 was a significant difference (X^, P<0.05) in the number of immature and adult geese infected with IS. clarkei.
Within individual sex and age groups immature males had the highest number infected, 9, comprising 42.9% of the infected population (Table 30). Seven or 78% of all infected males, were recorded as shedding oocysts, because oocysts were found in the wet smears or histological sections. There were 6 infected females,
28.6% of the infected birds, of which 4 (67%) were shedding oocysts.
Adult males had the fewest number of the infected population (2 or
9.5%), and none were shedding oocysts. Adult female geese had a total of 4 or 19% of all infected birds, 1 or 25% of which was shedding oocysts.
Histological examination of the snow goose kidneys collected revealed that two immature females collected had unidentified oocysts, presumed to be E^. clarkei, in the uriniferous tubles, 8.3% of the total examined. Endogenous stages were not observed in the other sections of the kidneys examined, and the wet smears of the opposite kidneys were negative for oocysts. All of the other snow goose kidneys were negative for the presence of coccidian oocysts and developmental stages. DISCUSSION
The recovery of Eimeria clarkei Hanson, Levine, and Ivens, 1957,
in the kidneys of Canada geese of the Mississippi Flyway clearly
establishes this parasite as a renal coccidian. For 24 years IJ.
clarkei * s target organ was not known nor was it reported from any avian species other than Chen c. caerulescens.
Material concerning E_. clarkei was extremely limited because
the coccidian had only been reported once. Even though IS. clarkei was recognized as a true species by most authors, some researches were skeptical of its status because the descriptions were made
from unsporulated oocysts from a single fecal sample, and because the oocysts were not seen again until Greiner et^ (1981) reported
the oocysts in fecal samples from Aleutian Canada geese.
The general classification for members of the genus Eimeria is as follows: the sporulated oocyst is tetrasporic and the sporocyst is dizoic, i.e., the oocysts contain four sporocysts each with two
sporozoites. (Fayer, 1980). Hanson et al (1957), though mentioning
they saw what appeared to be four sporoblasts in partially sporulated oocysts, essentially described unsporulated oocysts. Presumably because some of the oocysts did appear to have 4 sporoblasts, they placed the organism in the genus Eimeria and gave it a species name.
However, since the classification is not based solely on the morphology of the oocyst, but also the structure and location of the
108 109
endogenous stages, and host species, technically when the organism
was initially described, possibly it did not belong in the genus
Eimeria at all. Specifically because fully sporulated oocysts
were never observed, nothing was known about the endogenous stages
of the organism, and a list of definitive host species had not
been compiled.
Since the gross morphology of this coccidian so closely resembled
other anseriform coccidian species that did belong to the genus
Eimeria, Hanson et al (1957) were probably correct in their class
ification of the oocysts from the lesser snow goose. I believe
that E_. clarkei does belong in the genus Eimeria; however, because
fully sporulated oocysts have not been seen and because the endogenous
stages found in the kidney have not been differentiated, the class
ification of the organism is still only speculation.
The range of measurements given for IS. clarkei oocysts by
Hanson et al (1957) was somewhat larger than the oocysts found
in its Canada goose host (Hanson et al: 25 to 30 ym by 18 to 21 ym,
mean 27.3 by 19.3 ym); however, the size of the sporont was
approximately the same. The differences in oocyst sizes may be
because Hanson et al (1957) measured oocysts from a lone fecal
sample of a lesser snow goose and measurements recorded in my
study were made from oocysts taken directly from chilled or frozen
kidney tissue of several Canada geese. The difference in the two host species from which the oocysts was measured, the treatment of
the sample, the maturity of the oocysts, and the variation of the
oocyst from host to host could account for the slight differences
in size. 110
The measurements of 12. clarkei oocysts in Canada geese were very similar to those given by Greiner et al (1981), 23 to 28 -pm by
16 to 22 ym (mean: 26.4 by 18.4 ym). The similarities were also seen in the internal structures of the oocyst. Hanson eji al (1957) in their original description of E^ clarkei stated that the oocyst had no residuum or refractile granule; however, these structures were sometimes observed in unsporulated IS. clarkei oocysts found in
Canada geese and in Aleutian Canada geese.
Many authors who have tried to sporulate renal coccidian oocysts have had much difficulty. The same is true of E. clarkei. Hanson et^al (1957) tried to sporulate the oocyst they found and were not successful; therefore, they described an unsporulated oocyst.
Attempts to sporulate E_. clarkei oocysts found in thawed and chilled kidney tissue used in this study were also unsuccessful. Since the tissue had been frozen or chilled, this procedure could have killed the oocysts thus preventing sporulation. Another reason the oocysts did not sporulate may be that because they were removed from the tissue rather than the feces they may not have been mature enough to sporulate. Although there are several valid possibilities,
I feel the major reason oocyst sporulation was not achieved was because some environmental or physiological stimulus was not provided when I attempted to sporulate the oocysts. Kheysin (1972) pointed out that sporulation of oocysts in the external environment depends on three basic factors: humidity, temperature, and free access to oxygen. Thus sporulation of the oocysts can only be achieved by acquiring sufficient amounts of oocysts from fresh material, and by providing the required stimulus to facilitate sporulation. Ill
Though 13. clarkei and 13. truncata are both renal coccidians
found In Canada geese, the differences between the two species are
very striking. The more round bottomed 13. clarkei is somewhat
larger than the more ovoid 13. truncata according to the original
descriptions (14 to 22 ym by 11.7 to 16 ym). Although the reported
ranges for E_. truncata have been as great as 14 to 27 ym in length and 12 to 22 ym in width (Todd and Hammond, 1971), most of measurements
fall within the first group of ranges. The micropyle of 13. clarkei
is distinctly different from E^. truncata1 s more truncate end.
The geographical distribution of these two renal coccidians suggests that they might be allopatric species in the eastern flyways. Eimeria truncata has only been found in North American
geese that use the coastal flyways and not in birds of the continental flyways. Similar findings were reported by Walden (1961). While working with Anseriformes in Sweden, he also found that 13. truncata had a high prevalence in birds that used the coastal flyways in
Sweden. Why E_. truncata has not been found in Canada geese of the
Mississippi Flyway is not known.
Hanson at al^ (1957) pointed out that the geese in the south
Atlantic and Mississippi flyways are two different populations of
the interior subspecies of Canada geese, and even though they are the same subspecies, the geese of the Mississippi Valley Population are not infected with E, truncata. One reason for this could be that because the two subspecies utilize different breeding and wintering areas, there is little chance of contact between the
two subpopulations, thus limiting the transmission of E^. truncata to interior flyways. Possibly 13. truncata requiring certain environmental 112
conditions in order to survive, conditions that may not be present
in a non-coastal environment. Such a limiting factor would confine
13. truncata exclusively to the coastal flyways. The segregation
of these two parasitic species by factors such as these would also
'certainly reduce the competition between the species for suitable
hosts.
While the two subpopulations of Canada geese found in the
Atlantic and Mississippi flyways do not share any areas in any
portion of their flyways, the interior race of Canada geese in the
Mississippi Flyway does share a portion of its flyway with lesser
snow geese of the Eastern Prairie Population. Ironically 13. clarkei
was originally found in a fecal sample from a lesser snow goose
collected from Winisk, one of the areas where geese were collected
for this study.
If it is assumed that the lesser snow goose population was
initially infected with 13. clarkei and Canada geese were not, the
dissemination of the oocysts from snow geese to Canada geese that utilize these areas in upper Ontario is highly possible. This area would expose uninfected Canada geese to viable oocysts distributed
throughout the area by infected snow geese. Once infected, Canada geese would also contribute to the dispersal of the oocysts throughout the environment. Of course, the proliferation of the infection in the geese would depend mainly on the magnitude of the initial dose of 13. clarkei oocysts, whether the host had been exposed to the infection previously, or whether the bird's immunity system was capable of combating the developmental stages during the initial infection and upon reinfection. 113
Another point to consider is that because the areas which these two species share a common breeding area, with two infected populations distributing the oocysts throughout the environment, the probability of more susceptible, newly hatched geese contacting and acquiring IS. clarkei infections would be greatly increased.
Whether the infection is being distributed or disseminated at a higher rate by snow geese than Canada geese is difficult to prove because nothing is known of the prevalence or distribution of IS. clarkei in snow geese of the Eastern Prairie Population.
Unidentified oocysts presumed to be IS. clarkei were found in 8.3% of the snow geese sampled from Winisk, but the sample size taken was too small to warrant any definite conclusions.
Of the three locations sampled for this study, the Canada geese collected at Winisk had the highest number of infected geese collected, even though this area had the fewest number of geese sampled. The higher percentage of infection at the site located on the breeding grounds certainly suggests that there is a greater prevalence of the disease at that location but whether it is due to the influence of the snow goose populations in that area can only be postulated.
There were 11.6% of the geese infected with _E. clarkei at Winisk compared to 4.2% at Horicon and 7.3% at the two locations in southern
Illinois. One goose from Horicon died from renal coccidiosis caused by E^. clarkei and two immature males from southern Illinois showed gross signs of the disease. I do not think that these occurrences were indicative of the severity of the disease at the above locations.
I believe that because the prevalence of IS. clarkei infections were so low at each sampled location, the data does not allow a definitive conclusion regarding the infection pattern throughout the flyway. 114
The infected immature geese play a significant role in the distribution of E_. clarkei oocysts throughout the flyway. As stated previously, a higher percentage of immature birds was shedding oocysts into the environment than of infected adults, which had a much lower percentage actively passing oocysts. The high percentage of immature males (78%) and immature females (67%) shedding oocysts suggests that the immature age group is very important in the distribution of oocysts, perhaps even more important than the adult age group.
Generally young birds are usually more susceptible to initial enteric coccidial infections than older birds in domestic and wildlife situations. Walden (1961) stated that renal coccidiosis is mainly a disease of younger birds and reported a higher rate of infection in younger birds than in adult birds. Wobeser (1974) also reported significantly more juvenile ducks were infected with renal coccidia (Eimeria sp.) than adults. This observation was also seen in Canada geese infected with 15. clarkei. Significantly more immature than adult Canada geese were infected with this parasite (P<0.05). These data also point out the greater susceptibility of immature Canada geese to JE. clarkei infections.
The difference in prevalence of infection between age groups was not the only difference observed. Histosections of infected kidneys of immature and adult geese showed that the younger birds had a different cellular response to the infection than older birds. In adult birds, when the endogenous stages and oocysts of
15. clarkei were found, there was usually a cellular response of some kind in the form of infiltration of macrophages, and inflammatory 115 cells into areas where these stages were located (Figures 28, 29,
30). These cells seemed to surround and localize oocysts and gametocytes found in interstitial tissue, in tubular cells and in distended tubules. Such a leucocyte response to E^. clarkei infection was rarely seen in immature birds; only three of the total 15 infected birds of this group (20%) had significant cell mediated responses to the presence of oocysts and endogenous stages in the kidneys. However, 5 of 6 adult geese (83.3%) had some form of leucocyte infiltration in response to the infection. Most of immature birds (80%) probably did not have a macrophage response to the infection because they had no prior exposure to the coccidian, whereas virtually every infected adult goose showed a form of cellular immune response due to prior contact with the parasite.
Walden (1961) not only found that renal coccidiosis occurred more frequently in young birds surveyed in his study, he also found a seasonal difference in the prevalence of the disease. He stated that the fact that infections mainly affect young birds accounts for the increase in prevalence of infection during the summer and autumn months, when young birds are most frequently encountered.
His data also indicated the prevalence of infection in adult birds was twice as high during July to October than during November to
June. This suggests that there could also be a seasonal stimulus involved in the proliferation of renal coccidiosis.
Such a seasonal difference in _E. clarkei infections could not be demonstrated in my this study primarily because the birds were not sampled from early spring through the summer. However, the highest percentage of infections were found during the early autumn 116
season which corresponds to the samples taken at Winisk. Wobeser
(1974) reported that a greater percentage of female ducks were
infected with renal coccidia than males, but I found no such sexual
difference.
The endogenous stages of 15. clarkei observed in kidney sections
were of two types. The first type, as described in the results, was
probably the more frequent seen in infected kidneys. Initially, I
thought that these stages were early to late schizonts of E^.
clarkei because of the basophillic staining granules located
throughout the cell and because of the several nuclei observed
beneath the granules in some forms. The second type of stage was
presumed to be gametocytes because of the appearance of the nucleolus
and the localization of the granules to the periphery of the parasite
cell.
However, after comparing these stages with the stage of 15.
truncata described by Pellerdy (1974), and consulting other
researchers (Fayer, 1981, personal communication), I concluded that
the stages observed in the kidneys were probably gametocyte forms at
different stages of development but that they could not be classified
as schizonts, microgametocytes or macrogametocytes because of the
difficulty in differentiating the types observed. I feel that most
stages observed were probably early to late gametocytes because of
the structure of the parasite cells and the similarities between
the sporonts in the oocyts and most of the endogenous stages seen
in section. However, both schizont and gametocyte stages might
occur in renal tubule cells.
Postmortem changes that occurred in the tissue prior to fixation were a major factor that contributed to the difficulty in classifying 117 the endogenous stage observed. The geese from which kidneys were collected had been dead from 4 to 8 hours before they were fixed in formalin. Because the kidney is an organ that rapidly decomposes, postmortem changes in the tissue would not only affect the kidney tubule cells but also the intra- and extracellular parasite stages. Geese infected with 15. clarkei showed no symptoms of the infection upon collection and were virtually impossible to separate from non-infected birds prior to finding oocysts and/or developmental stages in wet smears or histo-sections. Thus upon collection it was not possible to separate infected from non-infected birds so fresh kidneys could be fixed to minimize postmortem changes.
Another reason the developmental stages of 15. clarkei are collectively referred to as endogenous stages is that without data from experimental infections to standardize the appearance and measurements of the schizonts, microgametocytes and macrogametocytes of E_. clarkei, any attempt to identify the stages observed in geese of this study would be speculation.
The life cycle of the renal coccidian 15. truncata has been studied extensively because of its importance as a disease in domestic geese. Pellerdy (1974) stated that the life cycle for
E_. truncata has not been completely worked out because there is no knowledge of how the organism gets to the kidneys from the intestine. However, he pointed out that from the work of early researches, it is known that IS. truncata is an exclusive inhabitant of the kidney. The life cycle for 15. truncata is probably as follows: the sporozoites are liberated from fully sporulated oocysts in the intestines and penetrate the intestinal wall where 118 they enter the capillaries. The sporozoites are then carried by the blood stream to the kidneys where upon arrival they penetrate kidney tubule cells. The schizonts, which measure about 13 ym in diameter, divide to give rise to many (20 to 30) sickle-shaped merozoites from 4 to 6 ym in length and 1.4 to 2 ym in width. It is not known if additional generations of schizonts occur, but several generations probably do follow the primary schizont generation if this life cycle is similar to the typical enteric coccidian life cycle.
Merozoites penetrate other tubule cells to form gametocytes.
Mature macrogametocytes range from 15 to 17 ym in diameter. The chromatoid granules predominate in the periphery of the cell. The microgametocytes do not stain as characteristically as macrogametocytes and are much shorter-lived, which explains perhaps why these forms are rarely seen. Ranging from 7 to 13 ym, the microgametocytes go through repeated nuclear division and produce daughter muclei which press towards the periphery of the parasite cell. Microgametes are produced and the slender, comma-shaped bodies, which seldom are more than 1 ym in diameter, swarm out of the host cell and fertilize mature macrogametocytes.
The fertilized macrogamete or zygote forms the walls of the oocyst with plastoid granules and ruptures the cytoplasmic membrane of the host cell upon maturity. The oocyst is passed from the kidney to the cloaca via the ureters with urates and other waste products filtered by the kidney. Sporulation takes place in the environment once the oocyst is expelled from the bird in the feces, and requires from 24 hours to 5 days before it is fully 119
sporulated and infective. A residual body is sometimes present in the oocyst.
The life cycle of J3. truncata is the only renal coccidian life cycle that has been demonstrated with any degree of success. I feel that the life cycle of IS. clarkei is probably very similar to the cycle of IS. truncata. The endogenous stages of IS. clarkei have been found in kidney tubule cells of Canada geese and the stages, measurements and appearances are very similar to those of IS. truncata.
Unlike E. truncata, however, no sporozites, merozoites, or microgametes were observed in kidney sections in this study. The reason for their absence could be that because these very minute bodies are so short-lived and sensitive to change, they could have died and decomposed prior to fixation and thus would not have been detected when sections were reviewed.
No experimental infections with E_. clarkei have been attempted because of its low prevalence and lack of recognition as a pathogenic renal coccidian. However, I feel that despite the absence of the sporozoites, merozoites and raicrogametes, and the differentiation of the endogenous stages found in Canada goose kidney cells, further research on the life cycle of IL. clarkei will demonstrate that it is quite similar to that of IS. truncata. CONCLUSION
This study was initiated to investigate two groups of poten
tially pathogenic parasites that occur in MVP Canada geese, gizzard nematodes and renal coccidia. This investigation showed an overall increase in the prevalence and mean burden of gizzard worms in this population of Canada geese since 1955. In addition, Eimeria clarkei was identified as the etiologic agent of renal coccidiosis in MVP
Canada geese.
Prevalences of gizzard worms were high in the Canada geese sampled, but the mean worm burdens were not extremely heavy.
Thus, large abundance index values for these helminths were not observed for this goose population suggesting a fairly healthy sampled population. Amidostomum anseris, A. spatulatum, and
Epomidiostomum crami were all present in the gizzard proper, however, each of these helminths were found occupying different areas of the organ. Amidostomum anseris was the most abundant gizzard nematode in all Canada geese examined and the pathologic effects of this species were not as severe as A. spatulatum or IS. crami, suggesting that the latter two species may have been incidental parasites in this host. Renal coccidiosis in MVP Canada geese was far less prevalent than gizzard worm infections, but the pathology associated with this infection was significant and in each case it was caused by IS. clarkei. These parasites were found to be totally
120 121
independent of one another, but they were both found in combination,
infecting the same host. Since gizzard worms are probably the most
common helminth parasite in Canada geese (Wehr and Herman, 1954),
the occurrence of light or moderate burdens of gizzard nematodes
in geese infected with renal coccidiosis was not unexpected.
The occurrence and response to gizzard nematodes and _E. clarkei
infections in immature and adult Canada geese differed significantly.
These results reinforce the concept that age is a significant factor
that affects the host's susceptibility to both of these parasitic
infections. These data also suggest that age as an interaction with area of collection also has a significant affect upon infection.
The breeding grounds in all probability serve as the main
focal area where MVP Canada geese acquire these parasitic infections.
I believe that the wintering areas are also areas where these
infections are acquired. These data also suggest that the lesser
snow goose population that interacts with Canada geese on the breeding grounds may also play a significant role in the acquisition and transmission of gizzard worms and renal coccidia. More research on the occurrence of these parasitic infections in the Eastern
Prairie Population of lesser snow geese is needed before definitive conclusions can be made.
The Pea Island studies provided significant information on the role of gizzard nematodes and renal coccidiosis in winter losses of
Canada geese. The studies conducted by Critcher (1950), Farr
(1954), Herman and Wehr (1954), and Herman et al (1955) were instrumental in demonstrating the correlation between high goose densities and poor nutritional health and increased susceptibility 122
to amldiostomiasis and renal coccidiosis. Lack (1954) also emphasized
the role of inadequate food supply and high bird densities as
predisposing factors when red grouse (Lagopus scoticus) were killed
by extreme burdens of Trichostrongylus sp.
Although the occurrence of gizzard worms and renal coccidosis
in MVP Canada geese was similar to this occurrence at Pea Island, I
do not feel that the status of these parasites in the MVP completely
parallels the Pea Island situation. The density of geese using
wintering areas in the Mississippi Flyway has increased considerably
in the last few years, but the overall nutritional state of the
population has not shown any significant decline because ample
amounts of desirable foods available in overwintering areas.
The importance of these etiologic agents will probably increase
if the densities of geese using available refuge lands continue to
increase. Should the nutritional status in geese of the MVP experience a decline in conjunction with the density increase, it is highly possible that various wintering areas used by this population could experience a parasitic disease situation much like
that which occurred at Pea Island. The stable nutritional condition
of MVP Canada geese certainly must be considered a major factor in reducing the hosts susceptibility to infections with these and other parasitic diseases. If the potential of such an outbreak is
to be minimized, the overcrowding of geese utilizing refuge land should be alleviated.
The occurrence and pathologic effects of gizzard worms and renal coccidiosis in MVP Canada geese given in this study will serve as baseline data for future studies that may be conducted. 123
While these findings indicate that at this time amidostomiasis, epomidiostomiasis, and renal coccidiosis are not major etiologic agents in MVP Canada geese, they should still be considered potentially important pathogenic diseases as management programs concerning this species are implemented on wintering areas* BIBLIOGRAPHY
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